I'm kinda doing a self-experiment right now with coffee dosages, using how scatter-brained I feel during meditation as indicator.

It's amazing how productive I believe I am when I drink coffee, yet my attention is all over the place and I think a lot of that feeling of productivity is placebo and/or chemically induced euphoria. Next I want to try tea to compare.

One thing's for sure: I used to meditate best, for longer and deeper, when I was taking dexamfetamine medication and was abstaining from coffee. Caffeine for ADHD is overrated and I will gladly die on this hill.