The reason they are all natural is there isn't any FDA requirments testing wise to give people what amounts to glorified juice and tea. Copious amounts of water and some vitamins to re-yellow the urine is all you need. You have to dilute the sample, but a truly diluted sample is clear. Clear samples scream dilution, and will get flagged for a specific gravity test.

You cannot "flush" your system. Cannibinoids are metabolized and stored in fat cells. Everyone on this planet wishes there was a magical solution they could drink that would "flush" their fat cells. All of those herbal products are just that. Herbs. Read the directions for any of those products and it always says to drink a ton of water. The herbs help re-yellow the piss, but the same can be done with vitamins.

B