Its promise is pretty appealing: no sugar, just a little caffeine, and a lot of vitamins to get you going. But are their claims too good to be true?
For many exhausted Americans, the idea of an instant energy shot is an alluring one. One of the most popular is the brand 5-hour Energy.
"5-hour Energy has seen huge growth in the last year. They control about 12 percent of the overall energy drink market, which is about $9 billion in sales," according to Natalie Zmunda of Advertizing Age.
The reviews are mixed:
"I think they definitely did something to stimulate you for awhile," says one tester.
"I didn't get a boost. I actually fell asleep on it," says another.
But these little bottles are making quite a big splash.
"They're really starting to go broad," Zmunda tells CBS News correspondent Michelle Miller. "It's not just men anymore; its men and women. Its 40 year olds, 50 year olds."
Commercials for the product downplay caffeine's role:
"It contains about as much caffeine as a cup of the leading premium coffee."
Instead, attributing the boost in energy to a special "blend" of vitamins:
"Its key ingredients can be found in everyday foods like avocados, broccoli, and bananas."
But some experts say these ads are misleading. "Energy is not obtained from vitamins or minerals.The feeling that you might get from this product is from the caffeine," says Dr. Tod Cooperman.
In fact, Dr. Cooperman of ConsumerLab.com ran tests on 5-hour Energy and found it has more caffeine than advertised.
According to the report, one shot contained 207 mg of caffeine. That's 15 percent more than the 180 mg of caffeine found in an 8 oz. cup of Starbucks Bold.
At up to $4 a shot, that's pretty expensive for energy that comes mainly from caffeine.
"The extra vitamins are not going to do anything for you," says Cooperton.
"The Early Show" took the findings to a representative for 5-hour Energy, but she stood by the advertised claims.
"The amount of caffeine is similar to what's in one premium cup of coffee and the amount of B vitamins are essential for the energy metabolism - and for boosting the furnace of the powerhouse of the cells to provide energy," says Dr. Kathy O'Neil-Smith of 5-hour Energy.
Because energy drinks are considered dietary supplements, the FDA doesn't require them to list caffeine amounts. So if that's a number you'd like to know, you're probably better off with a cup of joe.
CBS News Medical Correspondent Dr. Jennifer Ashton warns that too much caffeine can be especially harmful for teens and pregnant women. For the rest of us, taking in too much can lead to nervousness, insomnia, rapid heart beat, increased blood pressure and nausea.
For most people, 200-300 mg of caffeine - about two to four cups of coffee - is OK.
Also, when mixed with alcohol, energy drinks can lead to dangerous drinking. Some pre-mixed alcoholic energy drinks, like Four Loko, have been banned by the FDA.
If you're the type who needs an energy boost, there are other ways to increase your level of alertness.
Dr. Ashton says you can fight your afternoon fatigue with exercise - even a walk around the block may perk you up. Maintaining a healthy sleep schedule can also boost your energy, as well as a power nap.
If you're feeling sluggish, drink more water. Ashton says you may be dehydrated, which we tend to forget during the winter because it's so cold.
She also suggests having a small power snack of protein, like a handful of nuts.