The rules for eating and drinking during exercise are quite simple. For exercise lasting:
Less than an hour -- fit athletes do not need to take any food or drink, except they may need water on the hottest days.
More than an hour -- Take sugared drinks just before you begin and frequently during intense exercise.
More than three hours -- Take sugared drinks before you begin and frequently during intense exercise. Eat the food of your choice (fruit or sugar- added foods such as whole grain bars, etc.), plus a source of salt. We use potato chips or peanuts. You cannot get enough salt in a drink because it would taste awful.
More than five hours -- You need water, sugar, salt, and protein and lots of calories. Up to ten percent of the energy to power your muscles during exercise is supplied by protein stored in muscles. However, you do not lose enough muscle to harm performance during exercise until you have been exercising for more than five or six hours. Protein sources include whole grain bars, nuts, meat, fish, chicken, or dairy products.