If you drive to the south eastern most point of Bribie Island you will come to a gravel road about 500 metres long with a large turn around bay and plenty of open space at the end. There’s plenty of shady trees too. It’s only a short walk  from here down a sandy 4×4 track (emergency access only although you could drive down it if you want to risk getting in trouble). At the end of the track is an excellent secluded beach where you can fish, swim and drink beer. It’s a great place if you want to get away from the crowds. You may also be able stay the night in the carpark. Although there’s no camping signs at the start of the gravel road. I would say you could stop here a night, get up early and leave with no dramas from the ranger.