Many labs will discard a 'clear' UA as being diluted so take Vitamin B12 for color. Besides that they check for creatinine clearance too and if it's too low then they know that the patient has been drowning himself with water all weekend. They know all the tricks too.
Don't waste your money on those clearance kits, they serve little purpose. Buying a Walgreen's test before is a good indication of where you stand on the day. Never submit your first specimen of the day, it is concentrated and full of metabolites. Start drinking and take your Vitamin B12 or B2 and creatinine powder (or steak). Catch the specimen mid stream and then collect a reasonable amount, then finish in the toilet. Don't add water from the toilet to attempt to dilute. It will be likely that the water will be dyed blue anyway.
pH, creatinine, color, and temp must all match or it will be considered negative and thrown out. This, of course, will not look favorable to a prospective employer. Good luck. Come off all drugs that aren't covered by a prescription as soon as possible, exercise to speed up your metabolism, and there's no need to waste money on 'Cleanse' kits.