I make water kefir, have for many years. It doesn't have much sugar once the grains digest it all. It's not supposed to have quite as many strains as a dairy kefir but it's still very good I think.
Aerose - can you elaborate on kombucha? I am intrigued!
Kombucha has sugar so right away its poor. Also, it has a base of black and/or green tea which are histamines for those of us who have MCAS. Not to mention just the fact that it's fermented means high histamines.
The fermentation also produces yeast so if you have candida (most of us do) it provides a positive environment for candida to thrive on top of just the sugar. Finally, there aren't nearly enough probiotics to make it worth it. One probiotic pill has several times more probiotic without all the other downfalls