Please Help-Urgent! How to make Synthetic/Clean urine tainted with THC

[vox]

Swim is going to start being randomly drug tested, completely random on the spot. So he ordered some fake/clean synthetic urine for his drug test. The only problem is, swim must PASS for THC but FAIL for all other drugs (parents dont care about smoking, but they are on swims dick about his harder drug use) which presents a problem. Swim initially planned on getting some synthetic, clean urine but that wont work because swims parents know he smokes and will fail for the drug test for THC. So swim must fail for THC, but pass for all other drugs.

What if swim got the synthetic urine and added a little bit of a friends THC-only dirty piss. Would it show up on the test as positive for THC and negative for everything else? Or do you think mixing someones real/dirty (with THC) urine would conflict with the synthetic/clean urine and 'void' or mess it up in any way.

Also swim was thinking maybe leave a little bit of weed or kief in the bottle of synthetic piss to hopefully add THC to it.

Which one of these ideas do you guys think would work (if any)? Thanks.

Swim bought 2 test kits so he can have a friend mix his THC-laden piss with my synthetic clean piss and then test it and see what it comes out as. Swim is just worried that the fact that its mixing real human piss into the synthetic piss might fuck things up and/or void/fail the test.

If indeed that having mixing some dirty THC urine into swim's synthetic clean urine DOES cause a problem/doesnt work, swim was thinking maybe he could sprinkle some kief into the synthetic clean urine in an attempt to bring a failing result for THC.

Any help is much appreciated as this is a fairly serious matter for swim. Thanks in advance.