1 In a large mug, mix the flour, sugar, baking powder, and salt until well combined. Stir in the milk, melted butter, and vanilla until smooth. Scrape the bottom of the mug and stir in the sprinkles.
2 Cook in a microwave for 1 minute and 10 seconds to 1 minute and 30 seconds, until the cake is just set but still shiny on top.