Abstract: A device that allows a user to retain carbonation in conventional plastic beverage bottles for extended periods of time. In a first embodiment, a fluid impermeable, inflatable, elastic bladder is employed to fill the vapor space in the bottle when the beverage is dispensed. With the vapor space filled, the CO2 carbonization gases cannot dissipate. The bladder is removably attached to a nozzle cap. The nozzle cap incorporates an arrangement including an inflating tube that permits a user to inflate the bladder by simply blowing into the inflation tube.