Some do, but not all. AnswerParty!
An energy drink is a type of beverage containing stimulant drugs, chiefly caffeine, which is marketed as providing mental and physical stimulation. They may or may not be carbonated, and generally contain large amounts of caffeine and other stimulants, and many also contain sugar or other sweeteners, herbal extracts and amino acids. They are a subset of the larger group of energy products, which includes bars and gels. There are many brands and varieties of energy drinks.
Coffee, tea and other naturally caffeinated beverages are usually not considered energy drinks. Soft drinks such as cola, may contain caffeine, but are also not energy drinks. Some alcoholic beverages, such as Four Loko, contain caffeine and other stimulants and are marketed as energy drinks, although such drinks are banned in some American states.