Destem sour (tart) cherries. Get rid of damaged cherries or the ones with worms. Wash the remaining, destemmed cherries. (Optional: keep the stems for making cherry stem tea. Look in the accompanying text for insturctions.)
Layer sour cherries and sugar in the jar. Start with sour cherries, then generously cover with a few tablespoons of sugar. Repeat until you fill the entire jar.
Slowly pour liquor into the jar over sugar and tart cherries, as much brandy as the jar will take. This process takes a few minutes as the alcohol needs time to work through the cherries and sugar to fill up the remaining jar. Once you're done fasten the lid. Repeat for the remaining jars.
Take the jars outside, and leave them in a relatively (or partially) sunny place for at least 40 days, and up to 4-5 months. (The longer you ferment, the sweeter and better the liqueur will be!)
Once a week, stir the ingredients so that the sugar dissolves more easily. Open the first jar, and transfer a cup of cherries out of the jar. (Taking a cup of the cherries out first ensures the mixture doesn't spill out, as the jar is usually filled to the max.) Mix the remaining ingredients well with a long-handled spatula. Return the cherries to the jar and fasten the lid. Repeat with the remaining jars and return them to your fermentation spot.
After it's fermented, strain the cherry brandy into glass bottles. Keep the remaining sour cherries (although you can transfer a couple to each bottle with the liqueur) to use in a dessert or serve with the liqueur.
Serving: serve višnjevača with dessert, coffee, or as an aperitif. Storing: store for up to 2 years in a cool, dark place. Freezing: no!