upcoming drug test

so i have pretty much smoked everyday for the past year and a half, and i am entering a program in my school which i have to pass a drug test along with a physical and immunizations, etc. Anyways i have about 3 weeks to get the drug test done, i stopped smoking and have been drinking about a gallon to two gallons of water a day. Any advice on anything else to do to clean out, i am trying to pass this legit without having to use the synthetic stuff, but i think 2 weeks will probably be alright. But if any of you have any advice i am all ears, the rest of my schooling and my career are going to boil down to passing this pretty much.

How much do you smoke a day? What is your height and weight and physical activity level? Low fat high fiber diet can help and aerobic exercise. You can't wash out the metabolites so go easy on the water. Stay hydrated but don't over do it. Go ahead and order some instant tests online for a couple of bucks each.

i smoke about a half eighth a day probably, 5'7 about 200, but i have actually started working out the past few days, i was going to throughout to try to help clean out.