A beverage container for a carbonated beverage includes a floating hollow insert (1) comprising an upper moulding (2) and a lower moulding (3) defining a chamber for containing gas, a first one-way duck-bill type valve (4) integrally formed with the upper moulding (2) at the bottom of a down pipe (6) and arranged to allow gas to enter the chamber and a second duckbill valve (5) integrally formed with the lower moulding (3) and arranged to allow gas to exit the chamber and be jetted into the beverage upon opening the beverage container.