Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good concept, horrible execution

I have always been frustrated during the summer that I can't keep milk cold and fresh throughout the day for my daughter and would really prefer she not drink a ton of juice. So when I saw this product I was really excited. For about one week. Everything the other bad reviews say is true. It is very difficult to assemble in a way that won't leak. It is equally difficult to clean. And the sour milk smell that developed after a week of use (if you're out all day, the milk will eventually go bad) has made the cup totally unusable. I use a Thermos brand coffee thermos every day and don't have any of the same issues with that product. In fact, if they could just apply the assembly that they use on that mug to this cup they would probably have a perfect product. Until them, I am still in search of an insulated sippy cup. Don't waste your money on this one; it won't last long enough to be worth it.