lol I'm not even sure what probiotics are, but I don't know of anything that 'should' be taken during a fast. All drugs have side effects and most or all vitamins would interfere with a fast even if they weren't given in lactose or something similar. I do know that within the last couple of months since I have been here at least two other people have replied to other posts atesting to having cured their candida while fasting. I'm not sure how to search this forum yet but maybe you could try that and search for the keyword 'candida' and check out what these other people had to say.
One of my ex wives did have candida and hives and both were healed with proper food combining. I would suggest that you prepare for your fast with a cleansing diet for a few days at least then try fasting without additives. But first search for first hand reports of it's effectiveness on candida and then decide for yourself. :)