Begin drinking fluids immediately. Cold water also helps cool the body during exercise. Fructose, and drinks with more than 50 calories per serving, put sugar quickly into the body too quickly which slows the absorption of water and can cause nausea, cramps or diarrhea. Pop and fruit juices are not recommended during exercise because of the high sugar content. Carbonation can cause a feeling of fullness and stomach upset in some athletes.
Caffeine is a diuretic which can cause dehydration.