There is no real way to test clean for cocaine if the metabolites are in your body, a method that can buy you some time is dilution, drinking a lot of water in the few hours leading up to the test can possible dilute the concentration of metabolites in urine down below the cutoff levels of the tests. But this is risky business being as all approved labs are required to test for creatinine, PH, and specific gravity to classify a sample as actually being human urine. A dilute sample can be classified as an attempt to beat a urine test, and result in a positive test even if it says its negative. This usually occurs in a probation/parole/drug court setting. Pre-employment screens usually will retest, giving you more time to test actually clean. A good rule of thumb is a 3-5 day window for a non frequent light user. Heavy, frequent user, 6-9 days would be more accurate to pass a urine test for cocaine.