01 - Preheat oven to 350°F. Lightly grease a nonstick donut pan.
02 - In a large bowl, whisk together mashed bananas, milk, eggs, vegetable oil, granulated sugar, and vanilla extract until fully blended.
03 - In a separate bowl, sift together all-purpose flour, baking powder, baking soda, ground cinnamon, and salt.
04 - Gently fold the dry mixture into the wet ingredients until just combined. Avoid overmixing to preserve a tender crumb.
05 - Transfer batter into a piping bag or resealable plastic bag with the corner snipped. Pipe into the prepared donut pan, filling each cavity approximately three-quarters full.
06 - Bake for 12 to 15 minutes or until the donuts are golden and the tops spring back when gently pressed.
07 - Allow donuts to rest in the pan for 5 minutes, then transfer to a wire rack to cool completely.
08 - In a small bowl, whisk powdered sugar, milk, and vanilla extract until smooth. Dip cooled donuts into the glaze and set aside for a few minutes to allow the glaze to set.