In a microwave-safe mug, add the flour, sugar, and baking powder. Stir well to evenly mix the dry ingredients.
Pour in the nondairy milk, oil, and vanilla extract. Stir until a smooth, lump-free batter forms. Fold in chocolate chips or sprinkles if using.
Microwave the mug on high for 1 1/2-2 minutes. If needed, continue cooking in 10-second bursts until thoroughly cooked.