If you're a parent, have your kid (preferably of the same gender) piss in a container for you, and use theirs. I say this because in some labs the actually do a test to see if its even your piss. if its your kid it'll match up 50/50 and that's good enough for the piss test people.
Drug testing is not CSI. Drug testing devices only detect the presence of drug metabolites and have no ability whatsoever to determine the gender of the sample. The lab would have to perform genetic testing which is not only costly and complicated in process, but donors facing employment-related U/As are protected against genetic profiling under the Genetic Information Nondiscrimination Act of 2008 (GINA). That means the labs are prohibited from performing any form of genetic testing on urine samples collected for a drug test.

With that being said, any human urine sample will work as a sub as long as its completely drug-free.