Dampen a rag with water and wring it out. This will help prevent water spots.
If you're feeling fancy, you can soak the mug in warm water for up to 10 minutes. We won't judge you.
Use a soft-bristled brush or a gentle sponge to remove any remaining debris. Avoid using any abrasive materials, lest you wish to scratch the surface.
Rinse the mug thoroughly, then dry it with a clean towel. Do not use a microfiber cloth, as this will only lead to disappointment and despair.
Congratulations! You've managed to wash a mug without poisoning yourself. Pat yourself on the back.