Preheat your oven to 350°F. Grease a metal 9×5-inch loaf pan.
In a large bowl, combine the yellow cake mix, mashed bananas, vegetable oil, applesauce, eggs, and cinnamon. Stir until just combined; do not overmix.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.