First off I'm penguin_steeze but i'm banned right now :( I've personally passed a drug test this way. You will end up with diarrhea but you will pass. A short google search for "pectin to pass drug tests" will confirm this. I followed this post on grass city and I passed a drug test a couple months ago (smoked the day before and consecutive days leading up to the test. 5' 10" 145lb and fast metabolism)
I didn't follow the guidelines exactly because of circumstances but I did this:
Mix jello into 1 liter of water and drink 4 hours before the test. Then I drank 1 liter of water every hour except for the hour before the test. Good luck
Said post I followed
Gelatin is fruit pectin, and pectin is a very soluble fiber (i.e. is easily absorbed by water). These fibers have zero nutritional value, however the human body is very accustomed to them. Everything the human body takes in will eventually be released somehow. However, the manner through which this occurs depends on the substance taken in by the body. For example, you’re already well aware that the toxins left behind by marijuana find their way out through your urine. However, fruit pectin is an example of a substance released through a different method. To put it bluntly, you poop it out.
Why does this matter? Because another common trait of soluble fibers is their tendency to bind to fatty acids, such as bile. Bile is just an icky substance your liver excretes which aids in the digestive process by solubilizing lipids; in other words, by giving fat the ability to dissolve in water. This is where the magic kicks in. Since your body automatically sends fruit pectin to the colon, and fruit pectin binds to the acid which transports lipids (fat cells), the lipids which have absorbed the drug toxins are sent to your colon, and out your butt-hole.
To help all this make more sense, look at it from your body’s point of view. Under normal circumstances, your body finds it more efficient to send its lipids, and whatever they have absorbed, out through your urine. Understandably, it rejects the prospect of ridding itself of gelatin through the same procedure (imagine trying to piss Jell-O). However, if such a substance binds itself to the acids which transport your lipids, your body would much rather just send those lipids out with your poop. So in other words, this method works by temporarily compelling your body to poop out the toxins. Since no one is gonna be asking you for a sample of your poop (hopefully), you’re in the clear."
Use Sure Jell, and dilute with 1 liter 4 hours prior to test. Then drink another liter each hour for the next 3 hours.
Worried about color, take some B vitamins(B12) or vitamin C.
This will mask and dilute urine, but it still would not hurt if you detox for 5-7 days before test. It can work without if you are a light smoker, but if you got the time and not much cash, this is your best method other than substitution. Also, exercise and a healthy diet are never a bad idea.