The most effective drink for dehydration is an oral rehydration solution, which keeps roughly 25% more fluid in your body than plain water. But several everyday beverages, including milk and even orange juice, also outperform water for fluid retention. The best choice depends on how dehydrated you are and what caused it.
How Beverages Rank for Hydration
Not all drinks hydrate equally. Researchers developed a Beverage Hydration Index (BHI) that measures how well your body retains fluid from different drinks compared to still water, which serves as the baseline at 1.0. The higher the score, the more fluid your body holds onto instead of losing through urine.
After adjusting for water content, three beverages scored significantly higher than water: oral rehydration solutions (1.50), skim milk (1.44), and full-fat milk (1.32). Orange juice came in at 1.39 before adjustment but didn’t reach statistical significance after. On average, people who drank skim milk produced about 339 grams less urine than those who drank the same volume of water. For oral rehydration solutions, the difference was 362 grams, roughly a 25% decrease in urine output.
What these numbers mean practically: if you drink a glass of milk, your body holds onto a larger share of that fluid than if you drank a glass of water. That doesn’t mean water is bad for hydration. It works well for everyday needs. But when you’re actively dehydrated, drinks that contain electrolytes and some calories give your body more to work with.
Why Electrolytes Matter More Than Volume
The reason some drinks hydrate better than others comes down to what happens in your small intestine. Your gut has a transport system that moves sodium and glucose together into intestinal cells, pulling water along with them through osmotic pressure. When both sodium and a small amount of sugar are present in a drink, this system activates and water absorption speeds up considerably. This is the core principle behind oral rehydration solutions, which are specifically formulated to take advantage of this mechanism.
Plain water lacks sodium and glucose, so it relies on a slower absorption pathway. You still absorb the water, but your kidneys also clear it faster because there’s nothing signaling the body to retain it. Drinks with electrolytes and a bit of sugar essentially tell your body to hold onto the fluid longer.
Best Drinks by Situation
Mild Dehydration From Daily Life
If you have a dry mouth, darker urine, a headache, or muscle cramps, you’re likely mildly dehydrated. Water is perfectly fine here. Sipping steadily over an hour or two will resolve it. Adding a pinch of salt and a small squeeze of citrus to your water can help if you want slightly faster absorption, though for most people the difference is marginal.
After Exercise or Heavy Sweating
When you sweat heavily, you lose both fluid and electrolytes like sodium and potassium. Milk is a surprisingly strong option here. It contains sodium, potassium, carbohydrates, and protein in a combination that replenishes glycogen stores while retaining more fluid than water or most sports drinks. Skim milk in particular scored higher on the hydration index than any commercial beverage tested besides oral rehydration solutions.
Coconut water is another solid choice if dairy doesn’t work for you. It packs 594 mg of potassium per 12 ounces compared to just 47 mg in the same amount of a standard sports drink like Gatorade. The tradeoff is sodium: coconut water has about 94 mg per 12 ounces, while Gatorade has 166 mg. If you’ve been sweating heavily and losing a lot of salt, a sports drink or a combination of coconut water with a salty snack covers more ground.
Illness, Vomiting, or Diarrhea
This is where oral rehydration solutions (sold under brands like Pedialyte, DripDrop, or generic equivalents) genuinely shine. They’re formulated with the precise balance of sodium, glucose, and other electrolytes to maximize intestinal absorption. For vomiting or diarrhea, the general guidance for children is to replace about 10 mL per kilogram of body weight for each episode of watery stool, starting with small sips (around 5 mL every 5 minutes) to avoid triggering more vomiting. Adults can follow a similar slow-sipping approach.
Avoid fruit juices in high quantities during stomach illness. Their high sugar content can worsen diarrhea by drawing more water into the intestines.
What About Coffee, Tea, and Soda?
Caffeine has a mild diuretic effect, meaning it makes you urinate slightly more. But the fluid in a cup of coffee or tea more than compensates for that loss in most people. Research on caffeinated energy drinks found that even at doses up to 280 mg of caffeine (roughly two to three cups of coffee), habitual caffeine use didn’t change the diuretic response. Both regular and occasional caffeine drinkers had hydration index scores around 0.92 to 0.93 for caffeinated beverages, meaning they retained slightly less fluid than water but still came close.
In short, your morning coffee isn’t dehydrating you. But it’s also not the best choice when you’re already dehydrated and trying to recover. Stick with something that contains electrolytes in that situation.
Alcohol is a different story. It suppresses a hormone that helps your kidneys retain water, leading to significant fluid loss. Beer and wine are net negatives for hydration, especially at higher quantities.
Signs You Need More Than a Drink
Mild to moderate dehydration causes thirst, dry mouth, reduced urination, darker urine, headaches, cool dry skin, and muscle cramps. These respond well to oral fluids over a couple of hours.
Severe dehydration looks different: very dark or absent urine, shriveled skin, confusion, dizziness, rapid heartbeat, rapid breathing, or sunken eyes. One quick check is skin turgor. Pinch the skin on the back of your hand. If it slowly sags back into place instead of snapping back immediately, that suggests significant fluid loss. Severe dehydration requires medical attention, as oral fluids alone may not be absorbed fast enough to restore safe fluid levels.
A Simple Rehydration Approach
For most situations, you don’t need anything fancy. Start with water and add electrolytes if the dehydration is from exercise, heat, or illness. If you don’t have a commercial rehydration drink, you can make a basic version at home: mix about one liter of water with six teaspoons of sugar and half a teaspoon of salt. It won’t taste great, but it closely mimics the sodium-glucose ratio that drives faster absorption.
If you’re choosing a store-bought option, look at the sodium content. Drinks marketed as “electrolyte water” often contain trace amounts of minerals that make almost no functional difference. True rehydration drinks have noticeable sodium (at least 200 mg per serving) and moderate sugar. Pedialyte and similar products meet this threshold. Most flavored waters and “enhanced” beverages do not.