Chop the rhubarb into ½ pieces and put in a pot.

Cover the rhubarb in the pot with water, and bring to a simmer. I used about a liter of water.

Simmer until the rhubarb is very tender, then cool. I left mine overnight to steep, but you probably don’t need to.

Strain out the rhubarb. (When I stirred mine with a spoon, it disintegrated, making something like applesauce. I added honey and now we have a nice rhubarb compote.)

Add the honey and stir until dissolved. I used about ¾ cup, which made it very, very sweet. Keep in mind that the sugars will be digested to create the fizz, so you do want to start with it much sweeter than you would like the soda to be. Dilute the syrup with water if it comes on too strong (super tart, since it will get more sour as it ferments.)

Pour the “juice” into a sterilized demijohn, add your whey or sauerkraut juice and add your airlock.

Let it sit for about three days, and taste it. Mine fermented pretty quickly, but there are some variables– the temperature of the room, the strength of the culture you used, etc. Taste it and let it ferment until it’s only a little sweeter than you would like it to be.

Pour it into your swing-top bottles, and store in the fridge. You could leave them out at room temperature if you’d like to drink them sooner, but I usually pop them into the fridge to slow down the fermentation process. You will want to drink them within a week, or risk losing most of your Rhubarb Soda to the “geyser effect.”