Preheat oven to 350°F. Spray (4) mini loaf pans (3.25 in x5.75 in) with nonstick spray.
Whisk together the flour, baking soda, and salt in the bowl of a stand mixer. In a medium bowl, whisk the eggs and 1 1/2 cups granulated sugar together until combined. Whisk in the oil, greek yogurt, milk, and vanilla extract. Pour the wet ingredients into the dry ingredients, then mix until combined. Be careful not to overmix.
Mix the 1/2 cup granulated sugar and 1 Tablespoon of ground cinnamon together.
Pour half of the batter into the prepared mini loaf pans. It should be a little over 1/2 cup per mini loaf pan. Sprinkle a thick layer of the cinnamon-sugar mixture evenly over top of each mini loaf pan. Reserve a small amount of the cinnamon-sugar mixture to put on top of each loaf. Pour and spread the other half of the batter on top of the cinnamon-sugar mixture. Use the back of a spoon to spread it evenly. Sprinkle the remaining cinnamon-sugar mixture on top. Carefully, using a knife, make a large swirl down the loaf pans to create that nice swirl.
Bake mini loaves for approximately 40 minutes. This time will vary depending on the size of the mini loaf pans. The loaves are done when a toothpick placed in the center of the loaf comes out clean
Cool completely in the pans.