If sippy cups filled with milk sit in the sink, the milk spoils and it makes the whole cup and all the parts (valve, straw, etc.) smell bad. I’ve tried taking the cups apart and rinsing all the pieces and leaving them in the sink until I did the dishes, but I was afraid I would lose or accidentally throw away the small pieces. So I bought a plastic basket with suction cups on it (made for sponges) in the plumbing/bathroom section at Wal-Mart and after I rinse the parts I set them in the basket until I am ready to do dishes. The basket cost about $4.
Allie just emailed me to add:
The cleaning brushes made for Dr. Brown’s baby bottles are perfect for cleaning inside sippy cup parts.