In a large microwave safe mug, whisk together egg, vegetable oil, milk, and vanilla.
Whisk in flour, sugar, baking powder, and salt.
Stir in sprinkles.
Microwave on full power for 1 minute, or until cake tests done.
Serve and enjoy!
Notes
Every microwave is different. We have a 1250 watt microwave and my mug cake baked perfectly at one minute. Depending on your microwave will depend on the cook time! Adjust as needed.