At what age is it ok for children to drink energy drinks?

As with so many things there is no age, no amount etc that we can say is ok. Most parents will have opinions on what is appropriate, but none of us gets everything right with our children, and it isn't surprising that your neighbor might be offended by your suggestion, even though well intentioned.

I can't say there is anything "wrong" with what your neighbor is doing, not because I think it is ok to give kids red bull, but because it isn't that simple. When I talk of abuse, I usually mean something that is pretty black and white. It may well be that he doesn't realise the effect that red bull is having, and that what you see is something he could do better if he did understand this. However, you may have to accept that you can't help in this instance.

You haven't said if or how this is affecting you and why you are so concerned by it, so as well as considering your neighbors and their children, you may find it helpful to consider yourself too.