Generally it is most beneficial if you eat 1 to 2 hours before training. This keeps plenty of blood glucose available while your muscles are working. Good foods to eat before exercise are high carbohydrate choices which the body can easily break down to provide glucose to the muscles. These are foods like bananas, bagels and fruit juices. Dehydration will rob an athlete of needed stamina faster than any other single factor.
Extreme dehydration can cause permanent damage and in some cases, death.
Perspiration and exertion deplete the body of fluids necessary for optimal performance and lead to dehydration. It is important to drink plenty of cool water. If you don't like plain water, adding a small amount of flavoring, such as a powdered drink mix, may make it more palatable. Sports drinks offer no significant benefit unless you are engaged in sustained activity which requires carbohydrate replenishment. Consuming foods and beverages high in carbohydrates shortly after exercise will replenish your glycogen stores.