Preheat the oven to 350°F. Line the 9x5-inch loaf pan with parchment paper and generously spray with baking spray. Set aside.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

In a large bowl, whisk together the milk, vegetable oil, sour cream, sugar, egg, and vanilla until smooth.

Gradually fold the dry ingredients into the wet ingredients until just combined.

Mix 0.6667 cup of granulated sugar with cinnamon in a small bowl to make the cinnamon sugar mixture.

Pour one-third of the batter into the prepared loaf pan. Sprinkle with 0.25 cup of cinnamon sugar.

Repeat the layering with remaining batter and cinnamon sugar, finishing with a layer of batter.

Bake for 55-60 minutes, or until a toothpick inserted in the center comes out clean. Cool completely before slicing.