Want cheap?
Don't smoke or be around smoke for 4 days (includes your test day).
1st day - Drink TONS of water ALL day long, Pee 20 times if you need.
2nd day, Drink TONS of water ALL day long, Again, Pee 20 times if you need. Now your system should be flushed and your piss should look pretty much clear.
3rd day, Eat and drink what you always do.
Day 4, Piss in your cup and hand it over. Works every time and does not cost anything more than a normal day would.
Now, If this is a Piss/Blood test combo like they do so often now then you are screwed cuz it is in your blood much longer than your piss.
Hope that is helpful to you.
If you want a cleaner, Ready Clear is a well known brand. But the drinks are kinda a pain in the ass to deal with, Plus you still can't smoke for a couple days or it will not work.
Good luck
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