In a microwave-safe mug (that can hold at least 8 oz of liquid), add flour, baking powder, sugar, milk, oil, and vanilla. Mix with a small whisk until batter is completely smooth.
Stir in 1 tsp of sprinkles. Sprinkle remaining 1/2 tsp of sprinkle on top.
Cook in the microwave for about 1 minute, or until cake looks done. Let cake cool a few minutes before eating. Cake is best consumed right after the few minutes of cooling time.
NOTES
You can substitute with other types of milk but I found fat-free milk yields the best results.