Other caffeinated drinks (eg sodas) are either sweetened (sugar or HFCS or have artificial sweeteners.
So about a month ago I decided I was drinking too much caffeine. I'm talking 600-700mg a day. I should also point out that my variance with and without caffeine is pretty low. In college for example I tried once to take caffeine pills to stay awake to cram. Not sure how much I took but it was enough that my hands were shaking. I still fell asleep just fine. Some people really do seem a whole lot more sensitive to this than I am.
Anyway, my reason wasn't coffee in particular but sugar. For years I've drunk artificial sweetener sodas and ignoring any other possible side effects I think the big problem is that they still taste sweet so it seems like they still feed the craving loop for sugar without containing any sugar.
It's early days yet but I think I can already notice some difference. Like I had ice cream tonight that I've had many times before and it tasted too sweet.
Anyway I think it's impossible to talk about caffeine consumption without also considering sugar consumption because they really do go hand in hand.
Caffeine is a stimulant and seems like it can be used to enhance some activities including athletic ones [1].
[1] https://www.theatlantic.com/health/archive/2014/03/how-athle...