I'll chime in on this one for you.
The important distinction to make is whether you are using a sports drink (like Gatorade) used to rehydrate or an energy drink (like red bull). Watch out for the energy drinks, they contain caffeine and sugar. People sometimes use energy drinks during or after exercise to boost performance or rehydrate, but they have the opposite effect and can cause dehydration and electrolyte disturbances. Its not a bad idea to stay away from the energy drinks during exercise and if you use them at all, don't drink too many and don't mix them with alcohol. Red Bull is considered a health product in Canada and has directions for use on the label.
For hydration, water is just fine. Problem is people get bored of water and usually stop drinking it before they are actually rehydrated. Sports drinks don't really rehydrate a whole lot better than water. Sports drinks tend to taste better and the tartness of them encourages people to drink more, so you may hydrate better because you drink more.
If you are exercising for less than an hour water will do you just fine, but if you like the sports drinks, go ahead and drink them in moderation. Just remember the sugar content - do you really need it? If you're going hard for more than an hour or you're an endurance athlete then the glucose and electrolytes in the sports drink can be helpful. If you are not an endurance athlete and are thinking of starting training (marathon for example) check with your health care provider first.
What's most important, regardless of whether you choose water or a sports drink, is to rehydrate to replace fluid loss during exercise. Drink before, during and after exercise to replace fluid loss. And as you all know, increase your fluid intake when exercising in hot environments.
Exercise smart and eat smart.
