Everybody is always claiming that Energy drinks are full of caffeine. These people are talking without having any real knowledge on the subject.
In a can of red bull is around the same amount of caffeine as in 1 cup of coffee.
There is also caffeine in tea, it's not that bad for us. Just don't overdo it.
But most energy drinks contain a lot of taurine, that is where you get the energy boost from. And it's not healthy.
But 2 or 3 cans a day are fine for an average size adult.
There are also energy drinks with more natural ingredients.
Like ginseng. These can be less bad for you, but most of them still contain a lot of sugar.