I used to drink 6 cups of coffee a day - probably helped drive my adrenals into exhaustion, along with other things of course. I decided it was time to stop and tried to quit cold turkey which led into crazy headaches. The way I managed to quit was dropping the Caffeine to 3 cups a day, and 3 cups green tea a day. then the following week 2 cups of coffee and 2 of tea. I would drink half a cup of coffee then fill it with more half water to give me the illusion of drinking more cups. eventually I was down to 1 cup of coffee and 1 of tea. leading to 0 coffee 0 tea. it took about 3,4 weeks.
didn't get any withdrawal at all.
Now I manage to drink a couple cups of coffee on the weekend and keep it that way, just for the taste.
Some things you can't really quit cold turkey unless you're really strong.