Those that know me well know I have a terrible sweet tooth, and I love to drink Coke. A few years back my wife and I were on a diet of sorts, and she found a great drink recipe that we both still enjoy very much.
Get some seltzer water (we use Faygo) and some fruit juice (we use Cranberry). I like 25% juice to 75% water, very cold. It makes a sweet (but not TOO sweet) carbonated drink that I like just about as much as Coke. It has FAR less sugar in it, and no caffeine.