Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. Set aside.
In a large bowl, whisk the flour, baking soda, baking powder, cinnamon, and salt together. Set aside.
In a medium bowl, mash the bananas with a fork. Once mashed, whisk in the brown sugar, honey/maple syrup, coconut oil, egg, vanilla, and milk until combined.
Pour the wet ingredients into the dry ingredients and whisk until everything is just combined. Fold in the blueberries. Expect a semi-thick batter. Spoon the batter evenly into the muffin cups, filling them all the way to the top.
Bake for 5 minutes at 425°F (218°C); then, keeping the muffins in the oven, reduce heat to 350°F (177°C) and continue baking for another 15–18 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 20–23 minutes, give or take.
Allow the muffins to cool for 5 minutes in the muffin pan, and then transfer to a wire rack to continue cooling.
