Most Hydrating Drinks, Ranked by Science (Water Doesn't Win)

Ask almost anyone what the most hydrating drink is and the answer comes back instantly: water. So it surprises people that when researchers measured how much of a drink the body actually holds on to, plain water did not come out on top. Three drinks kept more fluid in the body, and two of them were not sports drinks or electrolyte powders. They were ordinary milk, skimmed and full-fat.

Here is the short answer. In the best-known study on this question, oral rehydration solution, skimmed milk and full-fat milk led to less urine than still water over four hours, which means more of the fluid stayed in. Most other everyday drinks, including coffee, tea, cola, juice, sparkling water and a sports drink, were not clearly different from water. Water was not beaten by everything; it simply shared a large middle group with most of what people drink.

Below: how the study worked, how each drink fared, why milk did better, where water still wins, and what to drink on an ordinary day, after a hard workout or with a stomach bug.

The Most Hydrating Drinks at a Glance

This table groups drinks by what the trial could actually show, rather than by individual scores, because the differences inside each group were too uncertain to rank one drink above another.

Group	Drinks tested	What the trial showed
Held more fluid than water	Oral rehydration solution, skimmed milk, full-fat milk	Clearly less urine than water over four hours
About the same as water	Cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water, sports drink	No clear difference from still water
Reference	Still water	The baseline every drink was compared with

Lists online often put a precise number next to every drink in a strict order. The study found only the top three reliably different from water, so a numbered chart makes small, uncertain gaps look real. This article sticks to what held up.

How Scientists Actually Measure Hydration

Your kidneys constantly balance how much water you keep against how much you pass as urine. When a lot of plain fluid arrives at once, part of it is passed again within a few hours. The fluid went in, but not all of it stayed.

A team of UK researchers set out to compare drinks on exactly that point. In the 2016 Beverage Hydration Index trial, 72 healthy men who were already well hydrated and had fasted drank one litre of a test drink over 30 minutes. The researchers then collected their urine for four hours. Each man tried still water plus three of the other drinks, so every drink could be compared with water in the same people.

From this they built the Beverage Hydration Index, or BHI. Still water is the reference and scores 1. A drink that leaves you passing less urine than water over the test period scores above 1, and one that leaves you passing more scores below 1.

The trial did not test women, children, older adults, dehydrated people, exercise recovery, illness or small servings sipped through a day. The results are real and useful, but they describe one setting.

What the Beverage Hydration Index Found

Held more fluid than water: oral rehydration solution, skimmed milk and full-fat milk. These were the only three drinks with a statistically clear difference from still water. People passed less urine after them, so more of the litre stayed in the body over the four hours.

About the same as water: everything else tested. Cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water and the sports drink all produced urine volumes that were not clearly different from water. Their scores sat a little above or below 1, but the trial could not separate those gaps from ordinary variation between people.

A few of these results go against popular belief:

Coffee and tea did not dehydrate the men in the study. The does coffee dehydrate you and tea and hydration guides go deeper.
Sparkling water behaved like still water, a point the sparkling versus still water article covers in detail.
The sports drink was not better than water at rest. The trial did not test long, sweaty exercise, which is what sports drinks are designed for.
Lager was not clearly different from water, which is not a reason to treat beer as a hydration drink (see below).

So the headline that "water doesn't win" is true in a narrow sense, but it needs the explanation that follows.

Why Milk and Rehydration Solution Beat Water

Milk topping a hydration chart makes sense once you look at what is in the glass. The study authors point to drink characteristics such as energy density and electrolyte content as likely influences on how much urine a drink produces.

Electrolytes, especially sodium. Oral rehydration solution is designed around a balance of salts and glucose, and milk naturally contains sodium and potassium. The body keeps water more readily when the salts that travel with it are also replaced, which is why WHO guidance on oral rehydration salts relies on a glucose and salt formula for diarrhoea.

Energy: sugar, protein and fat. Milk carries lactose, protein and fat, so it is far more energy-dense than water. The researchers list energy density among the features that can influence the urine response. Interestingly, the trial found no clear difference between skimmed and full-fat milk, so the fat alone does not explain the result.

In practice, milk is a reasonable choice when you want fluid plus some nutrition, for example after exercise, but not a reason to replace water all day. Oral rehydration solution is a tool for replacing water and salts lost through illness, not an everyday drink.

Where Plain Water Still Wins

If milk holds more fluid per litre, why is water still the default? Because retention is only one thing that matters, and on most of the others water wins easily.

No calories. Milk, juice and regular cola all carry real energy, and juice and cola carry a lot of sugar. If you tried to cover your whole daily fluid needs with them, a large part of your food energy would arrive in liquid form. Water lets you drink freely without touching your energy budget, which matters if you are managing your weight.

Cost and availability. Safe tap water is cheap and available almost everywhere. Nothing else on the list comes close on practicality.

It is enough for normal days. For steady, all-day hydration, the kind the daily water intake guide is built around, plain water does the job well. The advantage of milk and rehydration solution matters most after illness, hard exercise or heavy sweating, and much less for routine sipping through a normal day.

The honest takeaway is not "stop drinking water." It is "water is the right default, and a few other drinks are better tools for particular situations."

Drinks That Hydrate Less Than You Think

Stronger alcohol. The lager in the trial was not clearly different from water, but that does not extend to wine, spirits or several drinks in a row. Alcohol increases urine output, and the effect grows with the dose, so drinking more is a poor way to stay hydrated. The alcohol and hydration and hangover prevention guides explain the details.

Coffee, in context. A normal cup counts toward your fluid. Several strong coffees close together are a different situation, mainly for sleep and jitteriness.

Sports drinks, outside of sport. Sports drinks are designed to replace fluid, salt and fuel during long, hard or hot exercise. At a desk they are mostly sweetened water with no hydration advantage and an energy cost. The best electrolyte drinks compared guide covers when they are worth it.

Coconut water. It was not part of the trial, and the coconut water guide looks at what it does and does not offer.

A Practical Hydration Ranking for Real Life

Your everyday default: plain water, still or sparkling, whichever you prefer. It should make up most of your fluid. Tea, coffee and milk count toward your total too.

After hard exercise or heavy sweating: water plus a source of sodium, such as a salty meal, an electrolyte drink or a glass of milk. Long, hot sessions are where replacing both fluid and salt starts to matter. The athlete hydration guide and electrolytes 101 explain when and how much.

Recovering from vomiting or diarrhoea: a correctly prepared oral rehydration solution is the tool designed for this, because it replaces both the water and the salts you have lost. Milk, juice and ordinary sports drinks are not equivalent to a proper rehydration formula. Seek medical care if you cannot keep fluids down, if symptoms are severe or persistent, or if a baby, young child or older adult is affected. The guides on hydration when sick and how long it takes to rehydrate go through the steps.

For flavour and variety: tea, coffee in moderation, fruit-infused water and milk all count. Food counts as well: water-rich fruit, vegetables and soups add to your total, as the hydrating foods article shows.

When you want fluid without calories: plain or sparkling water, unsweetened tea or black coffee. Here the goal is not the highest retention score; it is fluid without sugar or energy.

Why Tracking Helps Here

The point is not to chase the most fluid-retaining drink at every moment. It is to reach a sensible daily total with drinks that suit your situation, mostly water plus whatever else you happen to drink.

This is where logging helps. Record the amount you actually drink, including water, tea, coffee, milk and juice, and think about nutrition separately. There is no need to multiply a drink by its BHI score: the index is a four-hour research measure, not a formula for your daily log. Water Tracker shows your real daily total instead of a guess. It cannot measure how much fluid your body retained or diagnose a hydration problem. If you also take electrolyte supplements during heavy training, keeping them visible in a companion app like Supplements Tracker makes it easier to discuss your intake with a clinician or dietitian when needed.

Frequently asked questions

What is the most hydrating drink?

In the main study on this question, oral rehydration solution, skimmed milk and full-fat milk kept more fluid in the body over four hours than still water. For everyday drinking, water is still the most practical choice because it has no sugar or calories and is easy to get.

Are there drinks that hydrate better than water?

Yes, in a narrow sense. After a large serving, oral rehydration solution and milk led to less urine than water in healthy men at rest. Most other common drinks, including coffee, tea, cola, juice and sports drinks, were not clearly different from water in the same test.

Is milk more hydrating than water?

In the trial, both skimmed and full-fat milk were retained better than water over four hours, likely because milk carries electrolytes and energy. It suits after-exercise drinking, but it also adds calories.

Do coffee and tea count toward hydration?

Yes. In the trial, coffee and both hot and iced tea were not clearly different from water, so a normal cup counts toward your daily fluid. Very large amounts of caffeine are a different matter, mainly for sleep and jitteriness.

Which drink rehydrates you the quickest?

For fluid and salts lost through diarrhoea or vomiting, a correctly prepared oral rehydration solution is the drink designed for the job. After ordinary exercise, water with some sodium from food or an electrolyte drink usually works well. If you cannot keep fluids down or feel very unwell, seek medical care rather than relying on any drink.

Is soda hydrating?

Cola and diet cola provide fluid, and the trial found them not clearly different from water. Regular soda, however, brings a lot of sugar, so it is a poor choice as an everyday source of fluid.

Conclusion

Hydration is about how much fluid stays in, not only how much goes down. In the four-hour Beverage Hydration Index trial, oral rehydration solution and milk led to less urine than water, while most other common drinks were about the same as water.

That does not dethrone water. Water remains the right everyday default because it hydrates well, costs little, carries no calories and is always to hand. The smarter approach is to match the drink to the moment: plain water for routine sipping, an oral rehydration solution when illness drains water and salts, milk or an electrolyte drink after hard exercise if it suits you, and everything else counted honestly toward your daily total.

What Are the Most Hydrating Drinks? Ranked by Science