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