False positive for cocaine on army drug test? Why?

For my weight issue I took these water pills called H2O Lean that day and a body cleanse drink called Herbal Clean Qcarbo or something a week prior. I dunno if those had anything to do with a false faint positive or not? If you have any idea why it would have happened or how I can prevent it from happening again before tomorrow please help! Also will senna pills affect it as well?