Line a mini muffin tin with liners, spray with non stick spray and set aside. Preheat oven to 375F.
In a medium-sized bowl, combine flour, baking powder, salt, and sugar. Whisk to fully combine.
Add milk, melted coconut oil, egg, vanilla extract and whisk to combine, being careful not to over mix. Just until combined.
Fold in rainbow sprinkles into the batter. You can leave a few extra to sprinkle on the top of unbaked muffins if desired.
Spoon batter evenly into muffin tins, about 2/3 of the way full. Bake at 375F for 10-13 minutes or until tops are golden brown and when a toothpick is inserted into the center of a muffin, it comes out clean.
Remove from the oven, and let cool in the pan for about 5 minutes, and transfer to a wire cooling rack to finish cooling the rest of the way.