Maybe on day 1. On day 100 you are simply immune to coffee and need to stop drinking coffee for 2 weeks to have any effect again.

Mate tea can also be am extra , when one is already mostly caffeine immune. Don’t know why, but it works (to a degree).

Don’t ask me, how I know.

Haha, joke is on you, that just makes me sleep even less.

Until your body builds up a tolerance and you need to keep drinking more and more to get the same high you used to from one cup.