Prep the pans and oven. Heat your oven to 350°F (175°C).
Grease three to four mini loaf pans (about 5 x 3 inches) or line with parchment slings for easy removal.
Make the cinnamon swirl. In a small bowl, mix 1/3 cup granulated sugar with 1 tablespoon ground cinnamon. Set aside.
Combine the dry ingredients. In a large bowl, whisk 1 3/4 cups all-purpose flour, 1/2 cup granulated sugar, 1/2 cup packed brown sugar, 1 teaspoon baking soda, 1/2 teaspoon salt, 1 teaspoon ground cinnamon, and 1 teaspoon pumpkin pie spice until well blended and no brown sugar clumps remain.
Whisk the wet ingredients. In a medium bowl, whisk 2 large eggs, 1 cup pumpkin purée, 1/2 cup neutral oil, 1/3 cup milk, and 2 teaspoons vanilla extract until smooth.
Bring the batter together. Pour the wet ingredients into the dry. Stir with a spatula just until combined. Do not overmix—a few small lumps are fine.
Layer with the swirl. Fill each mini loaf pan about one-third full with batter.
Sprinkle a generous layer of the cinnamon-sugar mixture over the batter. Add more batter to fill the pans to about two-thirds full, then finish with another light sprinkle of cinnamon sugar. Gently swirl with a butter knife in a few figure-eights. Don’t over-swirl or the layers will blend.
Bake. Place the pans on a baking sheet and bake for 22–28 minutes, or until the tops are set and a toothpick inserted near the center comes out with a few moist crumbs.
If using very small pans or silicone molds, start checking at 20 minutes.
Cool. Let the loaves cool in the pans for 10 minutes, then loosen edges and transfer to a wire rack to cool completely. The swirl sets as they cool, so resist slicing while hot.
Optional finishing touch. Dust with a little extra cinnamon sugar, drizzle a simple vanilla glaze (powdered sugar + milk + vanilla), or add a few chopped toasted nuts on top.