Do detox drinks work on marijuana?

No.
How these things ACTUALLY WORK, and not the "super magic herbal essence" way the labels claim they work, is by diluting your urine. (Remember, Spice is supposed to be some super magic herbal combination that gets you messed up naturally, and it's really oregano and flower petals someone sprayed with synthetic THC. I swear, they must think weed smokers are the dumbest people in the universe.) Look at the instructions on any of these things, and it says you're supposed to drink the $40 bottle of goo and then drink like four bottles full of water.

Some of them put other chemicals in the goo to try to fool a drug test. Creatine is a big one. The way you test for dilution is by looking at the creatinine level. Don't bother looking on the internet for normal creatinine levels because what's listed is the creatinine level for a kidney function test (if your kidneys don't work right, your creatinine level is going to be wrong--either too high or too low) and not a drug test. They know the creatinine level is going to be lower than normal because what's everyone do when they know they've got a drug test? Start slamming water so they can pee. But if they check for creatinine and there's none there. they know you've been playing around. You could either get called back in for another test or just flunked outright.

Detox drinks work IF and ONLY IF the tester uses dip-stick drug tests because you have to run a second test for adulteration and most people don't do it. If your parents think you smoke dope and they tell you "I'm going to give you a drug test tomorrow morning" then yeah, you might get lucky with a detox drink. (Memo to parents: if you decide to drug test your kid, don't tell him you're going to test him tomorrow morning, get him out of bed at 5:45am some morning and hand him a specimen cup, then watch him pee into it. The first urine of the day has all the best drug metabolites in it, so if he's hot it'll be really clear that he is.) But if you're testing with laboratory equipment, detox drinks are dangerous to you because a GC/MS machine can pick out the THC, the dilution and the other ingredients in the "pass your drug test" sludge.