So, if you weigh 115 pounds, and you smoke a small amount each day, and you have been clean for 28 days, you will probably pass.
I am 5’2″ and 112 pounds, and I passed a urine test after only 9 days of not smoking (I was smoking one to two bowls a day for years). But I also took one of those drinks (see the second Related Question below). So I’m not sure if I passed because I was clean, or because of the drink, or a combination of the two.
If you are taking a saliva or blood test, then you are definitely clean, as it takes a lot longer for your urine to be clean than your saliva or blood (see the first Related Question).
If you’re taking a hair test, however, then you are screwed, because hair tests can detect drugs years after you’ve taken them (although most only cut off a 1.5-inch sample of hair, which only goes back as far as 90 days), and there is no way to cheat or fool a hair test.