Why couldnt "SWIM" register here himself to ask this question?
Posting in the third person is frowned upon in these parts.

For starters, drinking water days before the test is of no help. THC is not water soluble like other types of drugs. It is fat soluble. THC is stored in the fat cells and remain there until the fat cells are burned for energy. When the fat cells burn, the THC metabolizes into THCA and gets released back into the bloodstream, filtered by the kidneys, and deposited in the bladder for the eventual exit. Drinking water only serves to dilute the THCA concentration that is present in the bladder. This phenomena is only temporary - once the fluids ingested had all been urinated out, a "dirty" donor would resume testing positive for THC. Therefore drinking fluids is only helpful on the day of the U/A.

Exercise is helpful if you have weeks to prepare for the U/A. But if you have been testing yourself with a THC test kit and it still shows a positive with 3 days before the scheduled U/A, then all exercise should be stopped, and put your body into "storage mode" until after the U/A. That way you wont be releasing a bunch of THCA into the bloodstream, which will end up in the urine to be detected.

Niacin is a myth. It does nothing to help rid the body of THC. The same goes with vinegar. Only time and exercise can rid the body of THC.