Heat oven to 400 degrees F. Coat a baking sheet with vegetable cooking spray.
Wash potatoes. Cut into thin slices, and place in large bowl. Pour oil onto the palms of your hands. Gently rub oil onto sweet-potato slices, tossing to combine. Sprinkle with sugar and cinnamon, tossing in bowl to coat evenly.
Place slices in a single layer on prepared baking sheet. Bake 20 minutes. Turn chips over and bake until slightly crisp, about 5 minutes. Transfer to plate; cool 5 minutes and serve.