The drinks are horrendously expensive so dont bother with them. I found this one, it looks good but have you seen the price, costs more or less the same as my kit which makes 5 litres...
Also the people at the place where I got the kit from told me these drinks are actually sterilised which presumably kills off some of the bacteria anyway but I dont know how true that is.
Kombucha tea is an excellent thing to take as an overall body detoxifier/balancer. Its not the same as EM...though it does contain some probiotic acids...lactic acid and acetic acid. I've tried it a couple of times, its quite detoxifying.
I have a really good comprehensive guide to everything Kombucha so if you're looking into it, get hold of that.. "Kombucha Tea For Your Health and Healing" by Alick and Mari Bartholomew.