Water is the obvious starting point, but plain water alone isn’t always the fastest or most effective way to rehydrate. When you’ve lost fluids through sweat, vomiting, diarrhea, or simply not drinking enough, your body also loses sodium and other electrolytes that help your cells absorb and retain that water. The best drink depends on how dehydrated you are and what caused the fluid loss.
Why Water Alone Isn’t Always Enough
Your small intestine absorbs water through a process that depends on sodium and glucose working together. A specialized transporter in the intestinal lining pulls one molecule of glucose and two sodium ions into the cell simultaneously. Water then follows passively through the concentration gradient those nutrients create. This is why drinks containing a small amount of sugar and salt rehydrate you faster than plain water: they activate this transport system and pull more water into your bloodstream.
This mechanism is the entire basis for oral rehydration solutions, which were originally developed to treat severe diarrheal illness. Even when the gut is actively losing fluid, the sodium-glucose transporter still works, making it possible to rehydrate by mouth in situations that might otherwise require an IV.
The Best Drinks for Rehydration
Researchers have tested common beverages head-to-head using something called the Beverage Hydration Index, which measures how much fluid your body retains over several hours compared to still water (scored at 1.0). The results are surprising: skim milk scored 1.58, full-fat milk scored 1.50, oral rehydration solutions scored 1.54, and orange juice scored 1.39. All of these kept the body hydrated significantly longer than plain water.
Milk works so well because it naturally contains sodium, potassium, and a small amount of sugar (lactose), plus protein and fat that slow gastric emptying, keeping fluid in your system longer. Sports drinks, despite their marketing, performed no better than water in the same research. They simply didn’t contain enough electrolytes to make a measurable difference in fluid retention.
Here’s a practical ranking for most situations:
- Oral rehydration solutions (like Pedialyte or WHO formula): best for illness-related dehydration involving vomiting or diarrhea
- Milk (skim or whole): excellent for everyday rehydration and post-exercise recovery
- Coconut water: naturally rich in potassium and comparable to low-calorie sports drinks in clinical trials
- Diluted juice or orange juice: good option, though full-strength juice is very sugary
- Water: perfectly fine for mild dehydration from not drinking enough throughout the day
Electrolyte Drinks: Pedialyte vs. Sports Drinks
Not all electrolyte drinks are created equal. Per 12-ounce serving, Pedialyte Classic contains 9 grams of sugar and 16% of your daily sodium needs. Gatorade Thirst Quencher contains 21 grams of sugar but only 7% of your daily sodium. That’s more than twice the sugar and less than half the sodium. Pedialyte Sport pushes the sodium even higher (21% of the daily value) while keeping sugar at just 5 grams.
This matters because rehydration depends on the right ratio of sodium to glucose. Too much sugar without enough sodium can actually slow absorption. If you’re rehydrating after a stomach bug, a hangover, or heat exhaustion, a product designed for medical rehydration will outperform a sports drink. Sports drinks were formulated to provide energy during exercise, not to replace serious fluid losses.
A Simple Homemade Rehydration Drink
You can make an effective oral rehydration solution with three ingredients from your kitchen. The University of Virginia Health System recommends this recipe: 4 cups of water, half a teaspoon of table salt, and 2 tablespoons of sugar. Stir until everything dissolves completely.
The proportions here are important. Too much sugar makes the solution hypertonic, which slows absorption. Too little salt defeats the purpose. Stick to the measurements rather than eyeballing it. This recipe approximates the sugar-to-salt ratio that activates the sodium-glucose transport system in your gut, and it costs almost nothing.
What to Avoid When Dehydrated
Drinks with very high sugar content, like soda, energy drinks, or undiluted fruit juice, can actually slow rehydration. These hypertonic beverages decrease the rate of gastric emptying and intestinal absorption, meaning the fluid sits in your stomach longer and gets pulled into your bloodstream more slowly. In some cases, especially with diarrhea, a very sugary drink can draw water into the intestine and make things worse.
Alcohol is also a poor choice. It suppresses the hormone that tells your kidneys to retain water, so you lose more fluid than you take in. If your dehydration started with a night of drinking, skip the “hair of the dog” and reach for an electrolyte solution instead.
How to Tell If You Need More Than a Drink
Mild dehydration, the kind where you have a dry mouth, feel thirsty, or notice darker urine, responds quickly to oral fluids. You should feel noticeably better within five to ten minutes of drinking. If you’re dealing with a headache, fatigue, or mild dizziness from not drinking enough water during the day, a glass or two of water (or any of the drinks above) will typically resolve things within an hour.
Moderate to severe dehydration is a different situation. Signs include very dark urine or no urine output, rapid heartbeat, sunken eyes, confusion, or dizziness that doesn’t improve after drinking fluids. At this level, oral rehydration may not be enough. Moderate dehydration often requires intravenous fluids, and severe dehydration is a medical emergency, particularly in young children and older adults who can deteriorate quickly.
How Much and How Fast to Drink
If you’re mildly dehydrated, sipping steadily works better than chugging a large amount at once. Drinking too fast can trigger nausea, especially if your stomach is already upset. Aim for small, frequent sips over 15 to 30 minutes rather than downing a full bottle in one go.
For exercise-related dehydration, a good rule of thumb is to drink about 1.5 times the fluid you lost. If you weighed yourself before and after a workout and lost a pound, that’s roughly 16 ounces of sweat, so you’d want to drink about 24 ounces over the next couple of hours. Choosing milk, coconut water, or an electrolyte drink rather than plain water helps you retain more of that fluid instead of just passing it through your kidneys.
For illness-related dehydration from vomiting or diarrhea, start with a tablespoon of oral rehydration solution every few minutes. If you can keep that down, gradually increase the amount. Trying to drink a full glass while actively nauseous usually backfires.