Going cold-turkey is never, ever, a good idea. Veeerry few people can manage cold turkey.

Can you make a plan about what you want to change in your diet? There's more than just Coca Cola.

Only change one thing at a time. Instead of cutting out ALL the Coke, try to drink a can or so less a day (I don't know how much you drink a day). If you buy bottles and not cans, then maybe try to drink less of the bottle at once (and record down how often you can drink it). After you do that for a while and it's easier, then remove some more. And then more. And then more.

It needs to be gradual so that you don't havve withdrawal symptoms, and also just to help you not notice the change you're making so your body can adjust.