'Energy Drinks' are a classification of functional drinks and the exact composition can and most likely will vary depending on what energy drink you consume. Always look at the label(s) to see what ingredients are in the energy drinks.
The most common ingredients include:
Vitamin B12 (Cobalamin) usually as Cyanocobalamin
Niacin (vitamin B3)
Pyridoxine (Vitamin B6)
Panthotenic Acid (Vitamin B5)
Riboflavon (Vitamin B2)
Other ingredients that are not common, but have been found in Energy Drinks, include:
Due to the caffeine content, it is generally accepted that energy drinks may acutely increase blood pressure (usually in the caffeine naive). However, a presentation at the European Society of Cardiology (2012) noted that after consumption of an Energy Drink containing Taurine that heart function increased despite increases in blood pressure.