Preheat Oven and Prep Pan:
Heat oven to 400°F (205°C). Coat a 12-cup muffin pan or a 24-cup mini muffin pan with non-stick spray, or insert paper liners.Whisk Wet Ingredients:
In a large mixing bowl, combine sugar, milk, yogurt, eggs, oil, and vanilla. Whisk until the mixture is smooth and fully blended.Add Flour Gradually:
Gradually add the flour, stirring just until incorporated. Avoid overmixing.Fold in Sprinkles:
Using a spatula, carefully fold in 1/2 cup of rainbow sprinkles until they are evenly distributed.Fill Muffin Cups:
With a medium cookie scoop, portion the batter into the 12 muffin cups, filling each about 2/3 full.Top with Sprinkles:
Optionally, top each muffin with the remaining 2 tablespoons of rainbow sprinkles.Bake Until Golden:
Bake at 400°F (205°C) for 10 to 15 minutes, until the muffins turn a light golden brown.Cool on Wire Rack:
After a couple of minutes, take the muffins out of the pan and set them on a wire rack to cool for 5 minutes prior to serving.Store Leftovers:
These are best when eaten fresh. Keep any leftovers in an airtight container for up to 2 days.