Oral rehydration solutions are the single most effective drink for treating dehydration, but skim milk is the best everyday beverage for staying hydrated over time. What works best for you depends on whether you’re trying to recover from active dehydration or simply maintain fluid balance throughout the day. The difference comes down to electrolytes, sugar concentration, and how quickly your body can absorb what you’re drinking.
How Drinks Are Ranked for Hydration
Not all fluids hydrate equally. Researchers developed something called the Beverage Hydration Index to measure how long different drinks keep water in your body compared to plain water. The index assigns water a score of 1.0, and anything scoring higher means your body retains more fluid after drinking it.
After adjusting for water content, only three beverages scored significantly higher than water: oral rehydration solutions (1.50), skim milk (1.44), and full-fat milk (1.32). Everything else, including sports drinks, cola, coffee, tea, orange juice, and sparkling water, performed about the same as plain water in terms of how much fluid your body actually held onto.
The common thread among the top three is electrolyte content. All three contain substantially more sodium and potassium than the drinks that matched water’s score. These electrolytes signal your kidneys to retain fluid rather than flush it out as urine.
Oral Rehydration Solutions for Active Dehydration
If you’re already dehydrated from illness, vomiting, diarrhea, or heavy sweating, an oral rehydration solution like Pedialyte is your best option. These drinks are specifically formulated with a precise balance of sodium, sugar, and water that takes advantage of how your intestines absorb fluid. When sodium and glucose arrive together in your small intestine, a specialized transport system pulls both into your bloodstream, and water follows along with them. This mechanism is why the right sugar-to-salt ratio matters so much.
Pedialyte contains about 370 milligrams of sodium and just 9 grams of sugar per 12-ounce serving. Compare that to Gatorade, which has only 160 milligrams of sodium but 21 grams of sugar in the same serving size. That difference is significant. Pedialyte delivers more than twice the sodium at less than half the sugar, which makes it far more effective for actual rehydration. Sports drinks were designed to fuel athletic performance, not to treat dehydration, and their higher sugar content reflects that.
Sugar concentration matters because drinks with too much sugar actually slow down fluid absorption. When a beverage exceeds about 8% carbohydrate concentration, it can cause gastrointestinal distress and delay gastric emptying. Many fruit juices and sodas blow past this threshold, which is why drinking apple juice when you have a stomach bug can make things worse.
Why Milk Outperforms Water
Skim milk’s strong showing on the hydration index surprises most people, but the science behind it is straightforward. A cup of milk provides a meaningful dose of both sodium and potassium, the two electrolytes most critical for maintaining fluid balance. It also contains about 8 grams of protein per cup, and that protein, along with the naturally occurring fat in whole milk, slows gastric emptying. Your stomach releases the fluid more gradually into your intestines, giving your body more time to absorb it rather than sending it straight to your bladder.
Skim milk slightly edges out full-fat milk for hydration, likely because its lower fat content means a higher proportion of the drink is actually water. Either way, milk is a practical choice after exercise or on a hot day when you want hydration that lasts. It’s not ideal during acute illness with nausea, but for everyday rehydration after a workout or a long stretch without fluids, it performs better than water, sports drinks, or juice.
Where Coconut Water and Sports Drinks Fit
Coconut water has a reputation as nature’s sports drink, but its electrolyte profile is lopsided. A cup delivers an impressive 404 milligrams of potassium, more than ten times what you’d get from a cup of Gatorade (37 milligrams). However, it contains only 64 milligrams of sodium compared to Gatorade’s 97 milligrams. Since sodium is the primary electrolyte driving fluid retention, coconut water is better for replenishing potassium after exercise than for rehydrating efficiently.
Standard sports drinks like Gatorade land in a middle ground that isn’t particularly strong for either purpose. They didn’t score any better than plain water on the hydration index, and their sugar content is more than double what you’d find in an oral rehydration solution. If you’re exercising intensely for over an hour, the carbohydrates in a sports drink can help fuel your muscles. But if your goal is purely rehydration, you’re better off with an oral rehydration solution or even a glass of milk.
When Water Is Enough
For mild dehydration from simply not drinking enough throughout the day, water works fine. Most daily dehydration isn’t a medical event. It’s the result of being busy, forgetting to drink, or spending time in warm weather. In these cases, sipping water steadily over an hour or two will restore your fluid levels without any special formulation. Adding a pinch of salt and a small snack alongside your water gives your body the sodium and glucose it needs to absorb that fluid efficiently.
The situations where plain water falls short are when you’ve lost significant electrolytes: prolonged sweating, repeated vomiting, diarrhea, or exercising hard for more than an hour in the heat. In those cases, replacing water without replacing sodium can actually dilute the sodium already in your blood, making things worse rather than better.
Making Your Own Rehydration Drink
If you don’t have a commercial rehydration solution on hand, you can approximate one at home. Mix about six teaspoons of sugar and half a teaspoon of table salt into a liter of clean water. This gets you close to the sugar-to-salt ratio that activates the sodium-glucose transport system in your gut. It won’t taste great, but it will rehydrate you faster than water alone. You can add a small squeeze of citrus for flavor without significantly changing the concentration.
Signs You Need More Than a Drink
Oral rehydration handles most cases of mild to moderate dehydration effectively, but severe dehydration requires medical treatment with intravenous fluids. Warning signs include a dry tongue and lips, no tears when crying (in children), dizziness when standing, confusion, rapid heartbeat, or very dark urine with little output. Left untreated, severe dehydration can lead to electrolyte imbalances, heat-related illness, and kidney damage. If drinking fluids isn’t improving your symptoms within a couple of hours, or if you can’t keep fluids down at all, that’s when the situation has moved beyond what any beverage can fix.