We are presented with a variety of sports drinks and it may be hard to pick one you like much less one that helps your performance. Some of the basic concepts behind hydration sports drinks are

• Maintaining body fluid levels to make sure systems function properly.
• Same for maintaining an electrolyte balance (i.e. replacing salts lost through sweating).
• Providing digestable sugars for longer duration training.
• Adding salts to enhance digestion of sugars (e.g. Gatorade)
• Adding proteins for faster after exercise muscle recovery.

Try on a longer ride or other workout to weigh yourself before and after. The difference added the weight of fluids consumed will give you a rate of fluid loss which will vary with the temperature and how hard you are exercising, but a rule of thumb is that you should be replacing water about as fast as you are losing it. Find brands you like and drink what will be served on race day. As you move into longer and longer races even finding liquids your stomach can tolerate can be difficult, a good reason to practice hydration during workouts.