Caffeine: Caffeine is a naturally occurring stimulant of the central nervous system and can be found around the world both naturally in coffees and in teas or artificially extracted for carbonates beverages. Its consumption can be done both recreationally or medicinally to improve alertness and enhance concentration. While it is often used in times of physical exertion, it is not meant to and cannot replace sleep.

Taurine: Taurine is an amino acid that your body naturally produces. It helps regulate heartbeat and muscle contractions, and energy levels. Usually your body makes enough that you don't need to supplement. It's thought, but not proven, that under stress conditions; like illness, physical exertion, or injury, the body does not create enough and supplements can help. Taurine might be a mild inhibitory neurotransmitter, some studies show it helps with excitable brain states. While this isn't exactly what we want, maybe it helps level us out so we function better with elevated levels of other stimulants.

Guarana: Guarana comes from plants in South America. Amazonians have used it for a long time to increase alertness and energy. It's more dense in caffeine than coffee beans (3-4% vs 1-2%). It's not just called caffeine because it contains a couple other things: theobromine and theophylline. They're found in coffees and teas, and are known stimulants. Marketing retards will sometimes call this one guaranine, as if it's something different. It's not.

B Vitamins: These are essentially the things that help you convert crap to energy. Crap like sugar, which is found in abundance in energy drinks. The jury's still out on whether or not they increase energy levels via supplementation, but they will sure help warding off the hangovers when you mix that energy drink with alcohol.

Ginseng: Ginseng, an adaptogenic herb, is known to increase energy, has some anti-fatigue components, and supposedly relieves stress. Right now it's suspected that gingseng helps stimulate the hypothalamic and pituitary glands, which then secrete something called adrenal corticotropic hormone. With a name like that, it can't possibly be bad. Ginseng is nothing that's naturally created by your body, so having this in your drink certainly won't hurt. 200mg/day seems to be the standard dose, but you can safely take up to 2700mg.

Ginkgo Biloba: It's suspected that ginkgo biloba is the longest-living organism on this planet. Using the theory that you get somethings (or someones) powers by eating the brains, eating the oldest thing on the planet is probably a good thing. Or maybe it's such a hardy mofo that it kill you instantly. But that's never been the case. It helps memory rentention, concentration, circulation, acts as an anti-depressant, and even shows signs of helping people with Alzheimer. The German government recognizes it as something that helps with memory loss, concentration, and depression. That's some kick-ass stuff right there. 60mg is a standard supplementation dose, and you can easily take 240mg. If you don't get this with your drinks, It's highly recommend supplementing your diet with it.

L-Carnitine: An amino acid usually created by your liver and kidneys, this stuff helps up your metabolism and energy levels. Because of the way it interacts with your body, it may act as a thermogenic and help increase weight loss and endurance during exercise. The jury is still out on whether or not you need to supplement unless you have an unusual diet, but you can take 2-6 grams without worry. Make sure you get L-Carnitine, which is the type your body creates and can use. L-Carnitine is inactive and may actually hurt endurance levels. Some people take this to support their heart, so putting it in an energy drink that increases your heart rate; good stuff.

Sugars: Glucose is the body's preferred fuel. That is why you get hyper with a lot of sugar. Energy drinks contain a ton of sugar. Therefore, energy. It's a carbohydrate, and a lot of exercise regiments suggest a good dose of sugar for workouts lasting more than an hour. A lot of athletes take it in the form of rice or noodles, so they have timed absorption. You can take a bunch of this easily; 150 grams in your system might get you wired, but probably won't hurt you.

Antioxidants: Antioxidants are things that help your body gracefully recover from the damage of free radicals. Vitamin C is an antioxidant, so claiming that your energy drink has a lot of antioxidants is like saying you're buying really expensive orange juice. But they're good, they help fend off illness and prevent cellular damage. Vitamins C and E, Vitamin A (aka retinol, beta-carotene), and selenium are all antioxidants.