Traditional Russian kvass has thousands of preparation options. This refreshing drink saved more than one generation of our ancestors from the summer heat. Kvass made from birch sap is one of the most famous recipes for homemade kvass. Adding raisins is a must here. There is wild yeast on the surface of raisins. They are the ones who start the fermentation process of birch kvass! Sugar will sweeten the drink and make it even tastier and more enjoyable!