Wash, peel, core, and slice apples. Hold slices in ascorbic acid solution to prevent discoloration.
Drain slices. Add 1 pint water or syrup per 5 pounds sliced apples and boil 5 minutes, stirring occasionally.
Fill hot jars with hot apple slices and liquid, leaving 1/2-inch headspace.
Process pints or quarts in a boiling-water canner: 20 minutes at 0–1,000 ft; 25 minutes at 1,001–3,000 ft; 30 minutes at 3,001–6,000 ft; 35 minutes above 6,000 ft.