Grease a medium skillet with oil spray and place it over medium heat.
Place a tortilla in the skillet, sprinkle the marshmallow halves and chocolate chips evenly over it. Top the filling with the second tortilla and spray it with oil spray. Cook the quesadilla for 1 to 2 minutes, or until lightly browned. Carefully flip it and cook on the other side for 1 to 2 minutes, or until browned.
Remove the tortillas to a cutting board. Sprinkle the cinnamon sugar over top, then cut the quesadilla into quarters.
Notes
Cinnamon Sugar Mixture: In a small jar, shake together 2 tablespoons sugar and ¾ teaspoon ground cinnamon. Cover and store at room temperature.