I have a customer that orders cakes from me for every occasion but she cant eat any of it because she is diabetic ( I would assume ) because she has requested a sugar free cake. I use box mix with pudding and sour cream and I know I can get a sugar free mix. I use wilton buttercream and MMF. Does anyone have any substitutions for what I am using to go sugar free or another recipe that I can use?

Thank you
Shawnteel

No idea how you could make sugar free fondant...but as for BC I've used this one which is good - you can't do a ton with it as far as decorating, but it tastes good.
http://allrecipes.com/Recipe/sugar-free-frosting/detail.aspx

I think you are SOL for sugar free fondant.