Preheat the oven to 425F. Line two muffin pans with 12 liners total, so every other cavity is empty.
In a large bowl, mix together the sugar, pumpkin puree, mashed bananas, oil, vanilla extract, milk, and eggs until smooth.
Add in the dry ingredients and fold everything together.
Scoop the muffin batter into the prepared liners. Fill them to the very top.
Mix together the cinnamon and sparkling sugar and sprinkle it over the muffins.
Bake for 5 minutes. Lower the temperature to 350F, without opening the oven door. Bake for an additional 16-18 minutes.