If you need the caffeine, you could try 5-hour energy. Some of them taste pretty gross (okay, most) but they're teeny, and they're only 4 calories. I'm a Pepsi addict, so I can totally feel your pain. Once I get over the initial caffeine withdrawls (the headaches are the worst part IMO), I don't think it's too bad being without it. It's more of a mental thing that I want it, especially with certain foods or at certain times. Good luck with getting through it!
I didn't know diet coke was caffeine free? They make it regular and caffeine free.
Anyway... for me... I made myself drink nothing but diet drinks ... took about 2 weeks or so for me to start enjoying them, but once I did... I could never go back to regular. They taste like pure syrup to me now.
I just think of soda like hummingbird food, pure sugar water. I'm a person, I don't need sugar water like a bird.
If you love the sparkle/fizz, I'd start mixing. 3/4 regular coke/diet. Then 1/2 regular coke/diet, then mostly diet with a little regular until you are used to the taste of diet. I used to hate diet soda too (the after taste was disgusting), now I like it okay. Some sodas are better tasting than others, diet Dr. Pepper is my favorite (I also like diet root beer and Crush diet Orange soda).
You can also start cutting back to 2 cokes a day, then 1 coke a day.
I don't really like Diet Coke either (although I can force it down)...I drink Coke Cherry Zero, Diet Barqs Rootbeer, and Diet Cherry Dr. Pepper and definitely prefer them (and all have our lovely, lovely friend caffeine). I also find that most diet sodas seem extra carbonated to me, and I don't particularly like it, so I never drink straight out of the can if I can help it. Personally, I like diet sodas much better out of a glass since the pouring helps get rid of just enough of the carbonation
I have a pretty violently nasty reaction to aspartame so when I gave up sodas I couldn't switch to diet (tried Pepsi One and just couldn't choke it down). I'm not a fan of regular water so I drink Nestle Flavored Water sweetened with Splenda. I'll admit that giving up soda was a huge issue for me but I managed to do it and now I'm good with it. You can do it too!