Will mega-t green tea supplements cause a drug test to be positive?

Not that I know of: unless they are testing for caffeine, which would rarely, if ever, be done. However, the label says that the ingredients are "proprietary" which means they don't have to tell you everything that is in it. However, I have never seen any reports of false positives secondary to any kind of tea. In any case, false positives on screening tests can be ruled out with confirmatory tests.