Hooray! I've just heard that Rebecca has some water kefir ready to send us - so soon I'll be able to ferment all sorts of different sweet drinks (assuming I can keep the kefir grains alive this time.)
In the mean time, my son and I have been fermenting apple juice using milk kefir. The apple juice is from our CSA and is very sweet and concentrated so it lends itself well to fermenting with kefir I think.
Opinion's divided over whether milk kefir grains can or should be used to ferment anything except dairy products. In Wild Fermentation, Sandor Katz writes that you can use them to ferment almost anything you like, as long as you give them some time to recuperate in dairy straight afterwards - so we thought we'd give that a go.
We've developed a system where we use half our grains to ferment apple juice, while the other half ferment milk or cream. Then we do another dairy ferment with all of the grains in together, then divide them in half again and go back to the beginning of the cycle.
I think that means that, taken over time, each milk kefir grain is spending roughly a third of its time in apple juice and the rest in dairy. (Any mathematically minded person able to confirm that?)
Here's some apple juice we fermented - with the grains still floating in it.
We call it our Cheat's Apple Cider. Apparently milk kefir can be very slightly alcoholic, so I suspect this apple juice is too, but only a little. When you take the first gulp, you get that warm feeling flowing through your veins ... but none of us have ever managed to get tipsy from it!