I think coffee, especially if there's sugar added, should be considered an energy drink. At their core, energy drinks are caffeine and sugar.
I just don't think we get things for free, whether it's medications, supplements, energy drinks, whatever. Introducing "energy" into the body increases dopamine levels so that you "feel" better, reduces adenosine levels so your neurons are firing more when otherwise they'd be relaxing, they raise your heart rate without the concomitant energy expenditure that would otherwise call for it, and bring more high-energy source into your body as sugars, which if you don't burn them up can turn into weight issues (if the energy drink contains artificial sweeteners, that brings in other dietary consequences).
The high levels of B-complex in an energy drink might actually work for you - if you're B-vitamin deficient. B-complex will help convert sugars to energy. On the other hand, if you have a requisite amount of B-complex in your bloodstream to meet your body's demands, the excess just passes out as urine. So that's the one thing that I think is relatively benign.
So me, I don't trust them. But in the interests of honesty, there have been two (2) days in my life when I was just dragging in the afternoon when work demanded that I be sharper, and I poured out a little (about a quarter can) of a co-worker's energy drink. It seemed to help, but I also think that it could've possibly been me just getting past a tired cycle anyway, or experiencing some psych/placebo effect. Who knows.