Preheat your oven to 350 degrees.
Mix together water, vinegar and baking soda. Combine with cake mix and eggs. Stir until well combined, and scrape the bowl with spatula.
Add the mashed bananas. Mix all with an electric mixer for 3 minutes at medium speed.
Pour into lined cupcake pan. Bake at 350 degrees for 35 minutes or until a toothpick comes out clean.
When cooled, frost with the Cream Cheese Frosting.
Mix together the powdered sugar, butter and cream cheese. Add in milk as needed to get the desired consistency for frosting. Mix in the vanilla.