Wash the cup with neutral detergent. The reason is that organic solvents will be used in the production process and may remain on the cups. Fill the cup with half a cup of boiling water, tighten the lid and turn it upside down. So you can see if the cup is leaking. The tightness of the cup is very important for heat preservation. The best tool for washing cups is a bottle brush. It is easy to clean the inner wall of the cup, and it is not easy to leave a dead angle.