I used to have a yeast infection, and splenda-sweetened products were what helped me to stay on my diet! Splenda, contrary to popular belief, will not make your candida worse unless you are sensitive to it in some way. A sip of diet coke shouldn't hurt you; just don't drink one every day because that Aspartame can do dreadful things to you in the long run. 1 can a week should be ok (that's what I did). One thing I would highly recommend to you for those times when you crave Sugar above all else would be Hershey's 1-Carb chocolate bars. Those actually fill you up (it's weird!) plus they contain inulin, a pre-biotic (in simple terms, it's a candy bar that's good for your digestive system! :). Another thing that's good is sugar-free ice cream, particuarily Breyer's. You will NEVER be able to tell the difference between the sugar-free stuff and the regular. It's that good!
Good luck curing your candida! :)