Step 1: Preheat your oven to 350°F (175°C).
Step 2: Grease a 9x5 inch loaf pan with vegetable oil or line it with parchment paper.
Step 3: Mash the overripe bananas in a large mixing bowl until smooth.
Step 4: Add sugar, brown sugar, vegetable oil, eggs, vanilla extract, and sour cream to the mashed bananas and mix well.
Step 5: In another bowl, whisk together all-purpose flour, baking soda, baking powder, whipped topping mix, and salt.
Step 6: Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined.
Step 7: Pour the batter into the prepared loaf pan, smoothing the top.
Step 8: Bake for 60-70 minutes, or until a toothpick comes out clean.
Step 9: Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.