What are you supposed to do with the jonny when it's full of wee?
A good supply of sandwich bags with handles that tie up. Much better.
Depending where you are, the handles can be left lose and the bag emptied through the window, or they can be tied tightly to produce very effective biological ordinance.
I caught a thermal over my old school last summer.
And before anyone starts: "...except water or fine sand carried for the purpodse of ballast..."!