A beverage preparation system for preparing beverages within a container by just adding water is provided. The beverage preparation system embodies an enclosure device forming a beverage admixture-filled enclosure with a permeable first membrane extending between first and second boundary elements. Attachment points may be disposed along the first and second membrane elements so as to enable formation of the beverage admixture-filled enclosure along the interior walls of the container by adhering the attachment points thereto. Alternatively, the enclosure device may provide a second membrane extending between the first and second boundary elements, forming a beverage admixture-filled reservoir so that the enclosure device may be received into and attached to any suitably sized pre-existing container. Whereby adding a suitable liquid to the container, the liquid permeates the first membrane so as to interact with the beverage admixture, resulting in a beverage mixture the user may drink from the container.
