Horses for courses and how long is "long".
Energy drinks have their place, particularly if you're pushing yourself (sportives, whatever) but are obviously not necessary for a 'round the block' pootle. I'm assuming you're asking about rides somewhere between the 2 but maybe closer to the latter?
I rarely rode sportives (but I did enjoy the maybe 8 or 10 I did) My riding was mainly morning rides of up to 50km, weekly rides of around 100km, and periodic longer/audax rides. I tended to average around 20kph, ride length and terrain dependant. Water served me just fine (with food in pockets for longer rides) for such rides. Maybe a pinch of salt added if it was going to be a hot day.
I've tried energy drinks but I don't get on with them. I find the taste, if only minimal, becomes too much/samey after a while and actually discourages me to drink. And that's a problem because hydration is important, you don't want to be discouraging that!
IMHO, most of us mere mortals, for the kind of riding we do, don't need energy drinks. Hydration, on the other hand, we do. But there's no law against them, and if you want to give them a try then do so, I'm certainly not going to be critical. In fact, it's probably the best way for you to answer your question - give them a go. It is, after all, what I did - I've only reached my conclusion by finding out for myself!