Without knowing anything else about your training and nutrition it's hard to give any type of input. But, ultimately, it sounds like you need more mental strength. If you're used to eating high sugar foods, it will take a while for your brain and body to get used to not eating them. You'll still want them though, and it's up to you to get past it and realize it's not a big deal.
That being said, if you can provide more info about your current daily nutrition it would be easier to give advice on how to curb some of those cravings. One question would be how much good fats are you getting in your day?