Preheat oven to 350°F / 177°C.
Spray a sheet pan with nonstick cooking spray.
Combine sugar and cinnamon. Set aside.
In a large mixing bowl, stir together cake mix, melted butter, eggs, and vanilla until just combined.
Spray a 1 Tablespoon measuring spoon with nonstick cooking spray and use it to scoop up even-sized portions of dough and roll them in balls. (Note: The dough is very soft, so just handle it gently; if the dough sticks to your hands, rub a drop of cooking oil between your hands before rolling the dough.)
Roll the dough balls in cinnamon-sugar to coat.
Place cookie dough balls on prepared sheet pan, leaving about 2 inches of space between them.
Bake cookies until cracks appear in the surface and the edges look firm, 9 to 11 minutes.
Let cookies cool for a few minutes on the sheet pan before transferring to a wire rack to cool completely.