I heard cranberry juice helps destroy bacteria in the bladder, is this true?

No: Studies found that when nursing home patients were given cranberry juice regularly, they had fewer bladder infections that the group that did not get cranberry juice. However, when patients with documented bladder infections were given cranberry juice, this did not resolve their infection. Bottom line is that cranberry juice may prevent bladder infections but did not treat the infections.

Yes: Cranberry juice acidifies the urine, making the environment inhospitable for many bacteria. I would not depend on it as a cure for a urinary tract infection though.

Not destroy but...: Cranberry juice is a good source of D-mannose, a sugar which does not destroy bacteria but which can cause one type of bacteria, E. coli (the cause of 90% of UTI's) to stop attaching to the bladder wall, allowing you to pee it out. But it is far more efficient to take pure D-mannose powder. See http://www.tahomaclinicblog.com/d-mannose-for-bladder-and-kidney-infections/