Preheat oven to 200°F (93°C).
Fill a large bowl with water and add vinegar. This will make a solution of "acidulated" water.
Core apples one at a time and then peel or leave unpeeled.
Slice apples 1/4" thick and place them into acidulated water.
When all the apples are sliced and placed into the acidulated water, remove apples in groups and blot between two clean dish towels to remove excess water.
Once the apple slices are blotted, place them on a lined baking sheet or on top of a drying rack that is placed into a baking sheet. Fill three baking sheets with apple slices.
Place baking sheets into the oven and close the door.
After two hours, rotate baking sheets to different oven racks. Check to make sure that no apples are sticking to their surface. If they are sticking, turn them over.
After 4 hours, check on apple slices. If any are dry, remove them. Continue to dry the remaining apple slices. It can take up to 6 hours to dry apples to a malleable consistency. Once all apple slices are dried to the desired consistency, allow them to cool.
Once completely cool, apple slices can now be placed into an airtight container and stored in a cool, dry place, such as a pantry. The shelf life is 2-3 months. Or, apple slices can be strung on a string if they are to be eaten within a few days.