We all know AA FAs do not have a career, most of them end up working in the aircraft aisles for the whole of their life. We all know USA based FA are generally very casual, and sometimes to the extremely casual. And we all know USA based FAs are primarily for your safety and well being on board rather than providing first class services. So, what is the problem here?
Coke Zero is not bad for your health.
But 3 cans of Coke Zero in 5 hours is excessive. That is 990ml of coke. Drink water, man.
If the FA remember that you are having the third can and reminded you by saying it is not good for you. I would say that it is damn good service! And least the FA cares and remembers what was served to you. That is what we call personal touch.