To quit caffeine, taper down intake slowly over a few weeks.

Caffeine pills (nodoz) are probably the best way to reduce intake slowly that I've done so far - easy to measure based on broken tablets.

There should be a product we could buy to do it because the progression would be satisfying in itself. Unfortunately one-off product categories never sell enough to make such a product profitable.

I've also done it slowly over a few weeks using instant coffee. It's a bit unpleasant at the end if watered-down because it's so weak. I also just reduced intake having the dry granules on a spoon (unpleasant but doable!)

Every few years I get bored of coffee shops or I get slight allergies to espresso coffee so I give up again.

Cold turkey gives me nasty headaches for far too long so I don't just stop any more.