High energy drinks have an amazing amount of caffeine (see the Wellness Support Group webinar on Energy Drinks).
The sale of drinks like coffee, sodas, energy drinks, and sports drinks is a multi-billion dollar industry. Water is essentially free and it flushes toxins out from the body. It lubricates and refreshes our body systems. It seems to me that it makes the most health and financial sense to stay with water. To learn more about the benefits of water, see page 210 in my book, There's An Elephant in the Room - Exposing Hidden Truths in the Science of Health.