Energy drinks use large quantities of caffeine and other stimulating ingredients like ginseng, guarana, and ephedrine to give an uplifting effect to the drinker. Containing about 80 mg of caffeine, the same as a cup of coffee, they also have a lot of sugar.
Many energy drinks also claim that the positive effects of the drink are results of the vitamins and amino acids in the fluid and that these vitamins are actually very beneficial to the body by detoxifying it and strengthening cardiac contractility. As with many foods and drinks, though, these effects are still being argued within the scientific community.
Energy drinks are not necessarily bad for your body; they will probably have about the same effect on you as a large cup of coffee or any other drink with that amount of caffeine and sugar would have. However, the educated and health-conscious person should be aware of exactly what effects these are and drink energy drinks wisely.