Eat Oatmeal before a long ride. Through in some raisins, blueberry's or strawberrys as you cook. Then top it off with a splash of honey and milk (preferably soy milk). During a long ride eat fig newtons, bananas, or take along a peanut butter and jelly sandwitch on whole wheat.

Do not drink diet sodas or tea as they will cause further dehydration.

Three things your body has to have:

1) Hydration - muscles don't work good without it.
2) Electrolytes (salts) - if you do not replace salts your body cannot use the water you may be pooring into it.
3) Energy - the fuel