Again, for the 1000x, don't listen to people who tout detox products here. There is no detoxing THC for the reasons stated as many times if not more. End of story, especially when it comes to qcarbo.

it seems that the detox products give you the B2 and the creatine and whatever else you need
No, that is not correct. Drinking something with creatine the day of the test will NOT help you pass the creatinine check. There is a difference between the two. Creatine needs 48 hours to convert to creatinine. So no, a $25+ bottle of colored water that has B2 in it is not worth it. Stick to creatine loading and simply buying some B2 at your drug store. There are absolutely, positively, no detox products that work.

As for the qcarbo or any detox drink for that matter, you can achieve the EXACT same result by opening the qcarbo, pouring it down the drain along with your hard earned money, and filling it one more time with water than the directions tell you to. If you didn't load up on creatine for a couple of days before the test and depending on how much you drank you'll score a negative/dilute which may or may not lead to another retest.