Last time i did one the rule was NO fluids!!! I think they were forced to change that one as someone got a record 16 hours to produce a urine specimen and that was after one of the CDT team "did something" to him to make him pee

depends on the team as well!! the one we had were fooking stupid!! they came onboard before breakfast and instead of saying no peeing at all when everyone woke up, didnt put restrictions in place until after breakfast!! Stupid really!! most people wake up slightly dehydrated with a fullish bladder so now it was empty bladders with people still slightly dehydrated now being expected to pee on demand didnt think that one through did they!!!