Kvas is an ancient refreshing bubbly drink, usually classified as "non-alcoholic".

It fits very well to any uncomfortably hot working environment - in the field, in the bakery, in the metallurgical factory.

Yeast:
Any yeast will fit. I used US-05 just because I have some leftovers. If no yeast is available - fresh bio grape will do the job. Grapes have some yeast on the skin. If no grape is available, 200g of yeast-free rye bread will be needed. In this case, natural rye yeast will come to play, it's like "lactobacillae", but acts slower, thus, more controllable.

Dosage:
Children - zero, however, some parents do increase dosage to up to 1L/day, if children are really helping out in the field or in the garden.
Adults - 10L/day. Some bakeries provide up to 5L/day, and set mandatory consumption to 1L/day.

Variations:
It's allowed to spoil the wort with any "lactobacillale". It will become even tastier, however, the better taste will last only 1-2 days, then you'll drain the vinegar to the sink. Children like that "acidy" type of kvas better than pure alcoholic one.

If you don't have access to Chocolate Rye malt, feel free to pick any rye malt, and bake it at 130C for 20-40 minutes. If no malt is available - please, use the rye flour.

Carbonization:
Carbonization is natural. That's why there is 100g sugar per 10L of drink. Feel free to replace it with 120g Honey, and you'll get "Honey Kvas".

Simplifications:
In some countries, Rye/Barley extract is available for the sale.

Bottling:
Please, avoid bottling. I ferment it in the bucket, and then we drink it straight from there. I pitch at 25C, and when primary fermentation is over, I add the sugar and put the bucket in the fridge. Next day the drink is cooled down to 10C and has some bubbles. That's sufficient.