Before I was forced to give it up, I easily drank a six pack of Diet Coke a day. I was afraid I would have terrible headaches if I gave it up cold turkey, so I started cutting back. I cut back to two a day for a few days, then one a day. I drank water in between. After a few days, I stopped all together. The second day, I woke up with a headache. I took about three sips of a diet coke. I haven't had one since and no withdrawal problems.