When do you drink if drug screen is the next day?

Lots and Lots of water! Make sure you drink a good few litres, above 3 and below 7 (watern posining occurs after 7/8 litres, causing swelling of the brain and subsequent death). Cocaine, Heroin etc, stay in the human body for 3 days. Whilst Cannabis remains in the body for 30 days! So be careful! ;)