Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Milk gets trapped and it smells!

Does this sippy cup keep milk cold? Yes. Does this sippy cup not leak? Yes. Does this sippy cup smell like spoiled milk after one month of use? Yes. There is a rubber gasket that hold the handles on the tumbler part of the cup. The gasket is not removable and milk gets trapped under it. I have tried several methods of cleaning including the bottle brush, the dishwasher, and shaking soapy water in it. Yesterday I took a paper towel and my fingernail and removed a lot of dried up milk. Disgusting! They now smell so bad that my son will not use them. What a disappointment! I did write to thermos to alert them of this problem. They sent me a canned response about not storing milk products too long in the cup. That's not the problem! This problem starts happening the first time a kid tips the cup up and milk gets under the seal. What a disappointment!