Don't try to look up how vinegar works because it is all too confusing. Vinegar and salicylic acid do damage the hair and allow the tide to get in to remove metabolites.

Sorry money is tight but if you can afford $10-15 ($4 for the activator, $3-5 for a packet of the bleach, $3-5 for a bottle of dye) you can buy the stuff to bleach your hair and redye it. Doing that would probably ensure you passing the test on top of everything else you have done.

PDX, read before you tell someone to shave their body head to toe 1 day before their test. Do you really think the hair test can be beaten just by shaving everything off? Do you think you are the first person to suggest this approach in error? They can also use nail shavings.