Mash the banana with a fork. Open and drain the pineapple. Measure out the walnuts. Set these ingredients aside.
Place the cake mix in a mixing bowl.
Add the cinnamon to the cake mix and stir to incorporate it into the dry mix.
Add the egg whites, plain non fat yogurt and water to the cake mix. Use a hand or stand mixer to beat all of the ingredients together.
Add the banana, pineapple and walnuts to the cake batter and fold them in so they are uniformly distributed throughout the batter.
Use a large scooper, and fill the foil lined cupcake tins. There should be enough batter for 24 cupcakes.
Place the cupcake tins in the oven to bake. Check the cupcakes at 20 min. You are looking for a toothpick to come out clean or the top to spring back when lightly pressed. If they are not quite done, bake an additional 2-3 min. My cupcakes baked for a total of 22 min.
Remove the cupcakes from the oven when done and let sit for 10 min. Transfer the cupcakes to a cooling rack to thoroughly cool, about an hr.
Serve the cupcakes and enjoy. Freeze the leftover cupcakes.