For the third year in a row, I make this kvass, a very pleasant drink, moderately sweet, carbonated with a pleasant note of coffee. It is made very simply, from available products. I'm sure you'll enjoy this refreshing drink.
Bring the water to a boil. Add sugar, coffee, stir, cover and cool to room temperature.
After cooling, add the yeast and citric acid and leave for 40 minutes. Pour into the bottles not to the top, but to leave about 6 cm from the cork, close the lid and send to the refrigerator for 12 hours.