I'm not sure that's true. You can buy caffeine pill over the counter. Energy drinks surely have nothing to do with food and everything to do with delivering caffeine and other stimulants. You can put vodka in a vaporizer and get stupid drunk in seconds. In these cases you have to ask if it crosses the line into being a drug that can be regulated.

E-cig makers, at least, can argue that e-cigs are a form of harm reduction. Maybe energy drinks, too, if they keep you from falling asleep at the wheel, but that's more tenuous.