There are no substitutes for probiotics. The best way is to start for awhile on about four strains of good, alive probiotics. Eventually,I was told to try some different strains but be careful as some produce histamine which makes you feel bad just like some food do.

Kefir grains contain live active cultures, so I would advise not heating it.

Given this is the candida section of the board, I would recommend assuring that you have no yeast sensitivity before investing time/$ into making kefir. I used to live with some folks that did great on kefir and would extol its benefits. No matter how I ingested it, early/late, empty/full - I had a sensitive response to the yeasts/microbes that it is riddled with! Just a heads up...if there is no sensitivity then it should be extolled!

Sandor Katz offers an interesting perspective about why fermented food/drinks are more than substitutes for probiotics, but their superiority because of ever evolving microbiology.

Enjoy.