Preheat your oven to 425 degrees F and grease a donut pan.
In a large mixing bowl, mash the ripe bananas with a fork or potato masher.
Stir in the dry red velvet cake mix until just combined.
Pour the mixture into a large ziploc bag or piping bag. Cut the tip off of one corner of the bag and pipe the batter into each donut cavity about ⅔ full.
Bake in the preheated oven for 7-8 minutes, or until the donuts are cooked through and a toothpick inserted in the donut comes out clean.
Allow the donuts to cool in the pan for 5-10 minutes before transferring them to a wire cooling rack.
Add the frosting to a microwave safe bowl and warm in the microwave for 10-20 seconds for a runny consistency to make dipping easier.
Dunk each donut upside down into the frosting and return to the cooling rack right-side up.
Follow immediately with sprinkles on top of the donuts before the frosting sets.
Allow to fully cool before serving, enjoy!
Notes
Use any cake flavor to switch up your donut flavors.
You can change the frosting on top to your liking, see my suggestions above.