Yes, they say that flushing your system with water when high as a kite on meth is a good idea as it gives your body the best chance of clearing out those metabolites.
Unfortunately, you may have left it too late, and I would be pretty surprised if you get away with this meth drug test. What are the repercussions of failing bro? I spent a month or so court ordered rehab. Was kinda boring as hell, but much better than goin inside, that's for sure. I was back using the 2nd day I was out though. No matter how good a job they do of getting you in a good frame of mind, if you get out and see your people and put yourself into the path of temptation, you'll be more screwed than ever.