What amount water do i drink to pass a drug test?

First of all, no: ethical doctor is, or at least should be, telling you how to falsify the result of a medical test. Second of all, one of the things measured in virtually all urine drug tests nowadays is the specific gravity and/or creatinine level, and this can show definitively if you have been water-loading, and your test will be voided. Some people will consider it a positive test. So, there is no amount.