Brown stains often appear on the insides of mugs due to tea, coffee, or other beverages. These unsightly marks can be stubborn and resistant to conventional cleaning methods. However, there are several effective techniques that can help restore your mugs to their original cleanliness without causing any harm to the material. Using natural ingredients like baking soda, vinegar, or lemon juice can be very effective. This guide will provide detailed steps to help you successfully eliminate these stains while ensuring that your mugs remain safe for use.