Drinking any fluid helps its just some are better than others.Any diuretics like coffee or good cause they make you pee. If you drink 40 -48 ounces of fluid the morning of the test you shouldn't get a negetive dillute. Dillution just means you're trying to get the total thc content in your urine below the 50ng limit by increasing the total amount of fluid that the thc is mixed with. You have the same amount of thc in your urine its just being mixed with 40 ounces of fluid verses maybe 5 ounce of fluid normally.