Fifteen seconds on Google turned up an unofficial forum for UPS workers. Pissing in bottles appears to be extremely common. From perusing a few threads on the topic, the zeitgeist appeared to be "everyone does it, but if you leave your piss bottles in the truck after your shift then you're an asshole".

https://www.browncafe.com/community/threads/what-do-you-do-w...

https://www.browncafe.com/community/threads/urine-bottles-in...

https://www.browncafe.com/community/threads/urine-bottles-le...

https://www.browncafe.com/community/threads/urine-bottles.36...