Okroshka? Yeah I love that stuff. I'm vegetarian, replacing the sausage with a vegetarian one (or leaving it out) works well. I followed this recipe:

https://www.youtube.com/watch?v=ifE7gDiLDbE

The Life of Boris also has a great video on making Kvass:

https://www.youtube.com/watch?v=k1UTJKBMvgc

though I haven't gotten around to trying it, I've only had commercial bottled and canned ones. I imagine if you make it yourself you'll have a slightly more alcoholic outcome.