Preheat your oven to 200°F (95°C). Line two baking sheets with parchment paper.

Wash and core the apples. Use a mandoline or sharp knife to slice the apples as thin as possible (about 1/8 inch thick).

Arrange the apple slices in a single layer on the prepared baking sheets. Make sure they don't overlap.

In a small bowl, mix the ground cinnamon and sugar (if using). Sprinkle the mixture evenly over the apple slices.

Bake in the preheated oven for 1.5 to 2 hours, or until the apple slices are golden and crispy. Flip the slices halfway through baking to ensure even crisping.

Turn off the oven and let the apple chips cool in the oven to get extra crispy.

Once fully cooled, transfer the apple chips to an airtight container for storage. Enjoy these tasty, healthy snacks!