Preheat oven to 375 F degrees. Line 2 large baking sheets with aluminum foil. Coat generously with nonstick cooking spray.
Thinly slice sweet potatoes into round discs, either using a mandolin slicer or large, sharp knife. Place all of the potato discs in a large resealable plastic bag. Add malt vinegar, seal and shake to coat. Allow to rest at room temperature for 15 minutes.
Discard liquid from bag. Arrange potato discs in a single layer on prepared baking sheets. Sprinkle with salt and coat with cooking spray. Bake for 15-20 minutes.
Remove from oven and flip potato discs. Sprinkle with additional salt. Bake another 10-15 minutes, until chips are crispy. Remove from oven and place chips on a wire rack to cool.
Store in an airtight container at room temperature.