GOOOOOd question

I dunno, I image any male water benders would do this anytime they where drunk

So while she doesn't specifically address urine, Hama does explain that the prisoners were kept in very dry conditions and that "any sign of trouble was met with cruel retribution." So even if urine provided waterbenders some liquid to work with, it really would not have been enough to escape. https://www.youtube.com/watch?v=91QbwtxQ6pY