Abstract: An inner container for a composite container for liquids in accordance with the known art, the improvement comprising a flexible bag-like container sealed around its periphery and having two socket members, one having the material of the container extending across its inner end as a frangible diaphragm, and the other providing a frangible diaphragm which, when broken, will permit the container to be filled with liquid, the two sides of the bag-like container being then sealed together to close the container.