Preheat the oven to 350°F.
Add the sugar, oil, eggs, vanilla, and banana to a mixing bowl and whisk together until the sugar has dissolved and the mixture is smooth and creamy.
Add the sourdough discard and stir until fully incorporated.
In a separate bowl, mix the dry ingredients. You'll need the flour, salt, baking soda, baking powder, and cinnamon. Once those are combined, add the dry ingredients to the wet ingredients. Use a spatula to gently fold them together until incorporated. Do not over mix.
Set the batter aside to rest for 10 minutes.
Add muffin liners to your muffin pan OR spray each muffin tin with nonstick cooking spray. Use a measuring cup or scoop to evenly fill the muffin tins ¾ full.
Bake for 25 minutes or until the muffins are light brown and fully cooked. You can insert a toothpick in the center of one to see if it comes out clean. If it comes out clean or with crumbs, your muffins are done.
Let the muffins rest in the pan for 15 minutes before removing them to a wire rack to cool.