Heat oven to 350° F. Grease the bottom of a 9x5x3-inch loaf pan.
In a large bowl, whisk the sugar, bananas, coconut oil, and vanilla until smooth. Stir in the milk and vinegar. Add both of the flours, baking soda, and salt. Stir just until combined. Pour into a pan.
Bake for 1 hour or until toothpick inserted into the center comes out clean, and a crack in the top of loaf appears dry. Cool 10 minutes. Loosen sides from the pan and remove loaf from the pan. Cool completely, about 1 hour, before slicing.
Notes
You can substitute the milk for a non-dairy milk to make this a vegan banana bread.You can use only all-purpose flour, but then decrease the milk to 1/4 cup.