1. Toothpaste: Clean the teacup with toothpaste. (As we all know, toothpaste is very white except for teeth (￣▽￣))
2. Baking soda: Pour hot water into the teacup, add baking soda to shake, and let it sit for a few minutes before pouring it out.
3. Salt: First prepare the salt water, then pour it into the thermos cup and shake it, let it sit for a while before pouring it out, and finally rinse it with water.
4. Milk: Pour half a cup of warm water into the cup, then pour a few spoonfuls of milk, shake it gently, let it sit for a few minutes, then pour it out, and then rinse it with water.
5. Orange peel: first clean the thermos cup with detergent, then put fresh orange peel into the cup, tighten the lid, leave it for about four hours, and finally clean the inside of the cup.
