Stir milk and vinegar together in a bowl; set aside to ‘sour’ for about 5 minutes.
Whisk flour, sugar, baking powder, baking soda, and salt together in a bowl. Whisk egg and butter into sour milk. Pour flour mixture into milk mixture and whisk until batter is smooth. Add cinnamon and vanilla extract to batter; mix well.
Heat a large skillet over medium heat and coat with cooking spray. Drop batter, 1/4 cup per pancake, onto the griddle and cook until bubbles form and the edges are dry, 3 to 4 minutes. Flip and cook until browned on the other side, 2 to 3 minutes. Repeat with remaining batter.