Saunas and niacin are nothing more than an old myth brought on by the father of the Scientology movement L. Ron Hubbard (do a Google search with the terms ''L. Ron Hubbard & Niacin" for more info. There you'll discover that Hub is nothing more than a crackpot with no medical training whatsoever and that anything coming from his mouth should be taken with a box of salt).

Also this is for probation so taking a detox isn't an option as they show up as a diluted test
And so does drinking "a hell out of some water".
BTW, drinking a bunch of water days or weeks before the U/A is of no help. THC is NOT water-soluble like other drugs. Its fat-soluble. Its stored in the fat cells and remain there until the fat cells are burned for energy. When fat cells burn, the THCA are released back into the bloodstream, filtered by the kidneys, and end up in the bladder. Therefore you cannot 'wash away' THC from your fat cells like you can wash away dirt off your car. Drinking water dilutes the THCA content thats present in your bladder. This phenomena is only temporary - once the water ingested had all been urinated out, a "dirty" donor would resume testing positive for THC. Therefore, drinking water is only helpful on the day of the U/A.

Samples are ruled "too-dilute" because the specific gravity and creatinine levels are below satifactory limits, therefore when doing any dilution protocol, youd have to take steps to ensure that these two urine constituents are maintained within acceptable limits. Read up on the Dilution 'sticky' thread.