Are you truly allergic, or fruit sensitive? I have been diagnosed with citrus allergies/sensitivity, yet am able to do the MC. The Master-Cleanse is not a fast without sustenance or calories. You get all the calories you need plus some important nutrients. Unless you are severly underweight, you can not possibly starve on the MC. As for the maple syrup there are substitutes.
Personally you sound like you could die of fear... I really suggest you see a doctor first...