When you are ready to make soda, sterilize your bottles. I do this by placing the bottles in a clean sink and pouring boiling water directly over them. When they are cool enough to handle, remove them to a clean surface.

In a large bowl or liquid measuring cup, whisk your whey and sugar into your juice until the sugar is fully dissolved.

Use a funnel to pour your juice mixture into your bottles. Seal the bottles tightly.

Leave on the counter at room temp to ferment. You should start seeing little bubbles forming in the soda within the first day or so.

I usually leave my soda to ferment for a total of 2.5-3 days. You can start tasting it after 2 days: it will get progressively less sweet the longer you leave it.

Burp (open the bottles to remove the first excess spurt of gas) the bottles once every 24 hours. You want to avoid explosions!

When your soda is fermented to your taste, move it to the fridge (still sealed tightly.)

Once it is chilled, enjoy! As you can see from the photo, this makes for an excellent Purple Cow.