Fill a quart-sized mason jar ½ to ¾ full with chopped apples, cores, peel, or scraps. Mix 2 tablespoons granulated sugar in 2 cups water. Stir to dissolve, then pour over apples. If apples are not fully submerged, add an additional cup of water mixed with 1 tablespoon sugar.
Cover jar with a coffee filter or breathable cloth and secure into place with rubber band or jar collar. Place jar in a cool, dark location (away from direct sunlight) and wait for the fermentation process to start. Stir mixture daily for the next two weeks. This will discourage mold growth, especially since some apples will float to the surface.
After 2 weeks, strain apples through a fine mesh strainer, and discard. Allow vinegar to ferment anywhere from 1 to 3 months. The longer you ferment the vinegar, the more the flavor will develop. Your finished vinegar should have a ph somewhere between 2 to 3.
Transfer finished vinegar to either flip-top bottles or bottles with tight fitting lids and store in a cool, dark, location.
Notes
If possible, choose a wide-mouthed jar, which will be easier to fill and work with.
During this time, bubbles will begin to form indicating that firmentation is in progress.
If you bottle the vinegar too early, the pressure will build up from the gases and you can end up with a mess on your hands.
Whenever possible, use organic apples and filtered water or unchlorinated water.
If you don't have enough apple bits and pieces to get started, you can save them up over time in the freezer until you're ready to start a batch of apple cider vinegar.
Don't use cheesecloth to cover the jar because fruit flies and other tiny bugs can get into the jar and ruin your fermentation.
The acidity in homemade vinegar can vary. For this reason, it's not recommended for canning purposes!