I would need over 24 oz of coffee for anything.
But at that point I'm pushing potentially unsafe levels..
I wish we were taught more about taking drugs. Use caffeine since it's legal, for an example.
"Don't have caffeine 2 days in a row. Ask yourself if you really need the energy or are thirsty/bored. Etc...."
You could apply the same to alcohol to reduce alcoholism.
Of course tolerance is also a factor. I’ve been reducing my intake, for a while it was well over 1g/day, and that wasn’t really about trying to “feel” anything.
(intentionally NOT quoting the remainder of your post)
The only time I ever felt anything from caffine:
I was working the midnight shift. (At a service industry job, there were no customers so it was dead.)
I took:
2 caffeine pills
4 coffee's
2 cans of coke
I was also surprised to learn while driving Truck, that some US States outlawed caffeine pills. (Ohio) It might have been available at a drug store though, I only had access to truck stops.