First of all, it depends on the appearance of the cup. See if the polishing of the inner and outer surfaces is uniform, whether there are bruises and scratches;
Second, to see whether the mouth welding is smooth and consistent, which is related to the feeling of drinking water is comfortable;
Third, look at the quality of plastic parts. Poor quality not only affects service life, but also affects drinking water hygiene;
Fourth, see if the internal seal is tight. Whether the screw plug and cup body fit properly. Whether it is free to spin in and out, whether it leaks water.
Fill the water upside down for four or five minutes or shake it forcefully to verify whether it is leaking.
Thermal insulation performance, which is the main technical index of insulating cup. Generally, it is impossible to check according to the standard when purchasing, but it can be checked by hand feeling after filling hot water. After two minutes, the lower part of the cup body will be heated, while the lower part of the insulated cup will always be cool.