Wash and chop the apples into chunks, or gather collected apple scraps (which can be saved in the freezer over time) and add them to your jar or other large fermenting vessel until it filled about halfway full.
Pour lukewarm filtered water over the apples into the container until it is almost full, but measure/note the total amount of water added.
Stir in sugar in ratios of 1 tablespoon of sugar per cup of water added, or for larger batches, 1 cup of sugar per gallon of water added.
Optional: Add a splash of finished organic apple cider vinegar (e.g. store-bought) to inoculate the culture and encourage fermenting.
Stir combined ingredients until thoroughly mixed, and cover with breathable material.
Store in a dark location around 70 to 75 degrees F for two weeks to ferment, and stir everyday to prevent mold from forming on top. If needed, add another layer of material like a dark towel on top of the container to block light.
After two weeks, strain and reserve the liquid into a similar sized container and cover again. Compost the apples.
Move the covered container of liquid to a location that is out of the way to continue long term fermentation. Maintain dark. A cooler "room temperature" at this stage is okay, but do not refrigerate yet.
After one month, sample the apple cider vinegar to see if it is finished fermenting and tart to your liking. If needed, allow it to continue to ferment for a total of two to three months.
Once it is fermented to your desired flavor, transfer the apple cider vinegar into bottles with lids (or swing top bottles). Store at room temperature or in the refrigerator, and enjoy!
Properly fermented apple cider vinegar should "stay good" for over a year - as long as it does not have visible mold, or a strong and unusual flavor or appearance.