I found this post that was helpfull for me.
Firstly, decide why you’re doing this. Do you want to get off caffeine? Is it the carbonation? Is it just the sugar? If it’s just the caffeine, then there are tons of alternatives. The same is true for people who want to limit the carbonation or cut their sugar intake. Whatever your reasons for restricting these items are up to you, but it helps to know what your goals are.
Secondly, choose substitutes. If caffeine is the item you want to limit, you can choose other sodas such as Sprite and Root Beer. If sugar is the problem, you can choose from a wide variety of diet sodas. If carbonation is what you’re trying to avoid, there are tons of flavored waters and juices to choose from. When I was quitting, I was avoiding all of the above and I wanted to limit my intake of artificial sweeteners, so I just stuck with water and herbal tea.
The next step is preparation. If you are going off caffeine, you’re going to have caffeine withdrawals and you won’t have much to turn to. I had headaches for four days in a row and no pain reliever that I took relieved any pain. What you are going to need is time. Expect to be a little under the weather for a week. Treat it like a flu or a cold. When you are tired, sleep. Give yourself permission to sleep twelve hours if you need it. You’ve been hopped up on sugar and caffeine for so long that your body is going to need to remember what it’s like to be awake naturally.
One thing that helped me was a rice bed buddy. I bought this one at a craft mall, but you can make one yourself. I’ve also seen them sold at Walgreen’s drug stores made into various shapes like booties, eye masks and shoulder covers. Mine is a simple piece of fabric sewn into a rectangle. Inside it is dry rice: simple. I just put it into the microwave for two minutes, wrap a towel around it (it will be very hot when it comes out) and lie down with it over my face. It smells a little like rice and it’s warm on my aching head and temples. It helped me go to sleep when I had the caffeine withdrawal headaches.
The next step is to listen to your cravings. I found myself craving pop when I was thirsty. I didn’t realize I was thirsty, I just thought that I wanted a Diet Coke. I drank about a gallon of water a day the first week. I don’t know if I had been dehydrated and my body was catching up on the water it needed or if I just used the water as a crutch to get past that first week. Either way, listen to your body.
Finally, remember that this too will pass. Some have reported caffeine withdrawals for weeks, others are able to get past the worst of it in a few days. No matter how long it takes for you, remember, there is an end to it. There must be some reason you decided to go off pop in the first place, concentrate on those benefits and know that the negative effects will wear off. Be patient with yourself.
How to Quit Soda Quicklist
1. Decide why you are doing this.
2. Find appropriate substitutes.
3. Be prepared by giving yourself extra time for sleep.
4. Stock up on remedies and substitutes.
5. Listen to your cravings.
6. Be patient with yourself.
Remember, this advice is never more useful than the advice of your doctor. Please contact your doctor if you plan on doing anything drastic with yourself. I haven’t noticed any drastic effects of being off caffeine, carbonation and artificial sweeteners except that water is far less expensive than Diet Coke. Good Luck!
Alright... Its time to kick coke... coke is like my lover, I'm gonna miss it.. Who is in?? 
