The natural choice for hydration is water. It hydrates better than any other liquid, both before and during exercise. Water tends to be less expensive and more available than any other drink. You need to drink 4-6 ounces of water for every 15-20 minutes of exercise. That can add up to a lot of water! While some people prefer the taste of water over other drinks, most people find it relatively bland and will stop drinking water before becoming fully hydrated. Water is the best, but it only helps you if you drink it.
Sports drinks don't hydrate better than water, but you are more likely to drink larger volumes, which leads to better hydration. The typical sweet-tart taste combination doesn't quench thirst, so you will keep drinking a sports drink long after water has lost its appeal. An attractive array of colors and flavors are available. You can get a carbohydrate boost from sports drinks, in addition to electrolytes which may be lost from perspiration, but these drinks tend to offer lower calories than juice or soft drinks.
Juice may be nutritious, but it isn't the best choice for hydration. The fructose, or fruit sugar, reduces the rate of water absorption so cells don't get hydrated very quickly. Juice is a food in its own right and it's uncommon for a person to drink sufficient quantities to keep hydrated. Juice has carbohydrates, vitamins, minerals, and electrolytes, but it isn't a great thirst quencher.
Carbonated Soft Drinks
When you get right down to it, the colas and uncolas of the world aren't good for the body. The acids used to carbonate and flavor these beverages will damage your teeth and may even weaken your bones. Soft drinks are devoid of any real nutritional content. Even so, they taste great! You are more likely to drink what you like, so if you love soft drinks then they might be a good way to hydrate. The carbohydrates will slow your absorption of water, but they will also provide a quick energy boost. In the long run, they aren't good for you, but if hydration is your goal, soft drinks aren't a bad choice. Avoid drinks with lots of sugar or caffeine, which will lessen the speed or degree of hydration.
Coffee and Tea
Coffee and tea can sabotage hydration. Both drinks act as diuretics, meaning they cause your kidneys to pull more water out of your bloodstream even as the digestive system is pulling water into your body. It's a two-steps-forward-one-step-back scenario. If you add milk or sugar, then you reduce the rate of water absorption even further. The bottom line? Save the latte for later.
A beer might be great after the game, as long as you were the spectator and not the athlete. Alcohol dehydrates your body. Alcoholic beverages are better for hydration than, say, seawater, but that's about it.
The bottom line: Drink water for maximum hydration, but feel free to mix things up a bit to cater to your personal taste. You will drink more of what you like. In the end, the quantity of liquid is the biggest factor for getting and staying hydrated.
Source: about.com/chemistry / photo from beginning nutrition