It's clearly a thing that some people have significant physiological effects from/dependency on and others don't. I like coffee in the morning but I'm also fine with black tea and even herbal tea. I've no reason to want to give it up but if I had to for some reason, I could do so tomorrow without any real issue other than annoyance on the same order as giving up cheese or something like that.

I like a cup of tea too, and I really like pepsi max, but after a while I'm perfectly happy with a rooibos tea, squash, fanta, fruit juice and there's nothing wrong with the occasional pepsi.