With names like Rockstar, Full Throttle and No Fear, caffeinated energy drinks are hot right now, accounting for about $744 million in annual sales. While they may especially appeal to young adults, the beverages often contain multiple stimulants, making them a poor choice for young children and pregnant women. They also can be risky if mixed with alcohol.

Consumer Reports recently tested a dozen carbonated energy drinks and found that some can provide a per-container caffeine jolt that’s the equivalent of two cups of coffee. Others can pile on the calories – up to 260 per can or bottle.

CR thinks the government should require companies to label caffeine content, but it doesn’t, so you often have no idea how much you’re getting. Caffeine levels in an 8-ounce serving ranged from 50 mg to 145 mg. By comparison, a cup of coffee has roughly 100 mg; a 12-ounce Coke about 35 mg. Caffeine intake up to about 300 mg a day is considered OK for most adults; children should be limited to well under 100 mg.

But most tested energy drinks have more than 8 ounces in a can or bottle. Anyone who guzzles the whole container consumes up to 200 mg of caffeine and up to 260 calories.

Celsius Energy Supplement, lemon lime, contained the most caffeine of the tested drinks at 145 mg per 8-ounce serving; and Archer Farms Energy Drink, fruit punch, (Target) contained the lowest at 50 mg per 8-ounce serving.

According to CR’s trained testers, all of the drinks tested sweet, and many were a bit bitter.

Two of the tested products – Celsius Energy Supplement and Enviga Sparkling Green – claim to burn calories, and in a few manufacturer-funded studies, healthy adults worked off about 100 calories more on average after drinking them than after drinking a placebo. Other claims can be nonsensical. Red Bull, for example, says it “improves performance, especially during times of increased stress or strain,” but high caffeine levels actually can cause anxiety.

CR’s take: The label “energy drink” makes these products sound healthful, and an occasional indulgence is fine for most people. But just don’t overdo it.