This is just one of my many pet peeves—opening a tupperware container that has been washed, yet still being able to smell an odour in it.
You can put the plastic container in the freezer for half an hour before using it and it removes the smell! I find this especially helpful if I am bringing a dish to a barbecue. For instance, I want to bring cupcakes, but the plastic smells like garlic. So, I pop it in the freezer for an hour and when I take it out, it no longer has the odour!