Gatorade is the ultimate hangover preventor. Have a couple of bottles on-hand at all times. Drink as much as you can before you pass out, and you’ll feel a lot better in the morning. It also comes in all sorts of flavors and colors with nifty names like "ION4" and "G SERIES".

We recommend that you only drink these type of drinks when you are dehydrated from doing sports, after a hard night of drinking, a bout of diarrhea, or the flu.  Otherwise, they contain a lot of carbs and if you're not active or dehydrated then you'll just help to increase the size of your gut. There are also beverages that contain electrolytes such as smartwater, which is basically just water with electrolytes added to it, without all of the sugar found in most sports drinks.

The reason that these sports drinks (gatorade/powerade/etc.) work so well is that they contain electrolytes.  These electrolytes help your body to absorb water faster than drinking water alone, this is why you always see sports teams drinking this stuff. In a nutshell, electrolytes help your body re-hydrate if you've lost water, which is a common occurence from any of the above mentioned situations.

If you're very active and do a lot of sports, the best time to down on of these is right after your workout. Also, keep in mind that if you're cheap or don't want the extra calories, water works just as well to re-hydrate. You will get hydrated faster by drinking electrolyte infused beverages, but you won't see a crazy huge leap in the speed that you're re-hydrated by drinking gatorade instead of water.