Hey there Ramona..
When I was fasting I had the same question. I went to Rite Aid and talked to a pharmicist and ended up getting what is called "Whole Source Dietary Supplements" - Which says it's "The Most Complete Multivitamin & Mineral With Herbs" supplement. (By Rite Aid) .. I DID NOT get sick while taking these during a Water Fast which was a surprise because like "High On Water" usually I would, no icky stomach feeling, nothing. I also took 500MG of Calcium (Rite Aid Brand) and Biotin for my hair. I'm not sure what others are taking, but this is what has been what I've stuck with on all my fasts. Hope this helps in some way. Oh, and the Whole Source from Rite Aid was pretty cheap too. I think for everything, it was under $20.00
However, High On Water may have a point.. maybe we don't even need anything? Not sure on that 100%.