Fruits and vegetables can provide the energy and stamina you need for physical exertion as well as mental focus and concentration. If you're looking for the ultimate fast food, juicing combines the best nutrients from a variety of fruits and vegetables for maximum energy and stamina. Fruits are packed with simple and complex sugars, carbohydrates, vitamin C, and B vitamins, all of which provide instant and/or sustained energy, as well as iron and copper, power nutrients that promote stamina and endurance.