preheat oven to 350. coat 18 muffin cups with cooking spray.
in a large bowl, combine cake mix, oil, pineapple, eggs and cinnamon. add enough water to reserved juice to make 1/2 cup, add it to a bowl them beat with an electric mixer until mixture is thoroughly combined.
stir in banana, 1/2 cup walnuts and 1/4 cup cherries mix well then pour into prepared muffin cups. sprinkle with remaining nuts and cherries.
bake 22-25 minutes, or until a toothpick in center comes out clean. let cool 10-15 minutes, then remove from muffin cups. let cool completely.