In a large bowl, whisk together the milk, yogurt, eggs, vanilla, and sugar, until smooth.
Sprinkle the flour over the wet ingredients, and then the baking powder, cinnamon, and salt over the flour. Gently start whisking the dry ingredients into the wet ingredients.
Mix the batter until you can not see any more dry ingredients, but making sure that the batter still contains small lumps. Rest the batter for 5 minutes while your waffle iron heats up.
When your waffle iron is ready, lightly spray the inside of the waffle iron with cooking spray and then scoop in some of the batter. Follow your machine's instructions, as they will all have different cooking times.
Once the waffles are lightly golden, remove from the waffle iron and place on a clean plate. Repeat the cooking process until the batter has been used up. Serve hot with your favorite toppings.