How can a zero calorie Red Bull or Monster be considered an "Energy Drink"?

Question

Calories is energy measured in joules, right? And Sugar is fuel. So Why on earth would you call it an energy drink when it has no Energy? 

Same goes for some sparkling water brands that clame to be energy drinks, but they too have no calories! Or Sugar!

Answer 1

0 calorie automatically doesn't mean zero caffeine .. 

Another example being Diet Coke which ironically has more caffeine than regular.

Answer 2

It's called caffeine.

Answer 3

They would be better described as 'stimulant drinks' They contain caffeine [just as in coffee], which gives a feeling of energy and wakefulness.