Gatorade or sports drinks are preferred over water because it keeps up you specific gravity, which if it is too low shows that you have been diluting. You should take Vitamin B-2 to add color back to your urine if visual is part of the validity testing, such as with a dipstick test. You can be clear though and still be valid. Multivitamins will NOT clean you out. Cranberry juice is only slightly helpful as it is a mild diuretic. It will not clean you out. If you are drinking enough sports drinks then you won't need a mild diuretic like cranberry juice. Start with about 64 ounces of fluid 4-6 hours before the test and every time you go to the bathroom, drink fluid to replace what was lost. Tums or Rolaids can be helpful too as well as salty foods.

You should do a home test today both with undilted urine and diluted urine. If you can't pass, substitute.