The Master-Cleanse has lots of Sugar in the form of maple syrup. If you have a Sugar sensitive metabolism, that could have triggered a blood Sugar issue. In his book, Burroughs recommends that diabetics use blackstrap molasses instead of maple syrup. I think that should be extended to hypoglycemics and others who are sugar sensitive.
Sounds like you normally eat healthy, so perhaps the Master-Cleanse is not for you. If you want to fast again, you might try a veggie juice fast, using mostly "above ground" veggies.
To get the cravings back under control, you need to avoid fruit juices, simple carbs and sugars in all forms. Consider eliminating all grains for a while, though as a vegetarian, that is a hardship. Try drinking diluted pure cranberry juice or diluted lemon juice instead of lemonaid to eliminate the sweet flavor.
Good luck! Sugar cravings tend to go with mood swings, so be gentle with yourself till you get back in balance.