Seems that the Bieber was in an NYC night club when he felt the urge to relieve himself, and, taking things into his own hands, he relieved himself into a janitor's bucket.

Or did he? I have compelling evidence that Justin Bieber did NOT urinate into the Janitor's mop bucket. Conclusive evidence, that on that evening in New York, the cleaner's bucket was unsullied, and the pop scrotum did not, in fact, pee into the said bucket. 

http://perezhilton.com/2013-07-11-justin-bieber-bill-clinton-apology-advice-after-bucket-peeing-incident#.Ud7PpYx-_IU

http://www.avclub.com/articles/justin-bieber-takes-seriously-artistic-piss-in-a-m,99954/