Trying to pass a meth drug test the day after taking meth is liking trying to brush up on some algebra the night before an advanced calculus exam: There's no point.
If you're still struggling with the basics of algebra with less than 24 hours to go, then you may as well give up home and go home.
The same applies for trying to pass a meth test if you've ingested or inhaled methamphetamine in the past 24 hours.
Depending on what kind of test this is (UA, blood, hair, saliva) and how accurate the lab work is, meth may stay in your system for weeks, if not months.
"Flushing" it out with water will be ineffective, and there are no miracle cures out there - just rip off merchants trying to make a quick buck out of people too panicked or high to see a scam coming.
So my advice is to come clean, and get clean! There's not other way brother. That kind of drug messes with your head in a way you DO NOT need.