There are many types of energy drinks in the market, some are emphasized hydration, muscle recovery, antioxidants, etc. the key ingredient for energy drinks is caffeine. Caffeine can increase concentration & refresh. Most energy drinks will add around 150 to 160mg of caffeine in each bottle.Overtaking caffeine will have side effects on the human body. Nowadays, some energy drinks are using natural caffeine, such as green tea, Guarana, but even the caffeine is from natural plants, taking the appropriate caffeine dosage every day still is the most important while drinking energy drinks.