Abstract: Systems have a first container and a second container removably joined by an intermediate member, the intermediate member forming a partial seal for the first container. The intermediate member includes an attachment area including a fastener for removably attaching the second container to the intermediate member. The attachment area and fastener are configured so that a portion of an upper surface of the intermediate member is accessible and visible to a user when the second container is attached to the intermediate member. In systems where the first container holds a liquid, the intermediate member includes a puncturable area for a straw or other conduit, and may include indicators for different drinks.