Eat every few hours. It takes your body a couple of hours to break down the sugars in food, so nibbling will keep you from crashing.
Drink water. Losing just 2 percent of your body's H2O can decrease energy levels by 20 percent, according to Charlie Ryrie, author of The Healing Energies of Water.
Snack on fruit or peanut butter. Fruit breaks down slowly, keeping blood sugar levels steady, and high-protein snacks like yogurt or peanut butter are good sources of amino acids, which help keep energy levels high.