A better strategy would be to urinate at least 3-4 times prior to the scheduled U/A.

BTW, If the worries youre experiencing will not go away, you can always cut to the chase and use your roomates clean pee as a substitute, if passing the U/A and securing that new job is of any real importance to you. Employment-related U/As are not observed unless you had been suspected of tampering.

For subbing tips, read up on the Substitution "sticky" thread.