1/2 cup pitted, chopped cherries or 1 cup fresh, whole and uncracked cherry pits*
If you haven’t pitted the cherries yet, start there. Do so over a bowl to catch the juices that are bound to drip and drop during the process. Those juices are tasty delicious and stain easily, so you don’t want them going to waste and splattering all over the place.
Simply put the 1/2 chopped cherries or 1 cup fresh, whole and uncracked cherry pits in a glass jar or other seal-able container (jars are preferably to bottles here since you’ll need to get everything out again when you strain the vinegar), fill it with the 2 cups cider vinegar or white wine vinegar, cover, and set aside overnight to let the cherry flavor blend into the vinegar.
Strain, discard the cherries and/or cherry pits, return the vinegar to the jar or transfer to a bottle, cover or otherwise seal, and store at room temperature for up to a year. Use cherry vinegar in salad dressings, in glazes, or mixed with sparkling water or club soda and a bit of honey or sugar to taste for a refreshing soft drink.
* Again, be sure to use only whole cherry pits and to discard them after the soak. Cherry pits contain cyanide, a poison, and you certainly don’t want that in the vinegar.