Embodiments of the present disclosure include a cap for a container that incorporates a receptacle for an additive. The cap can enable separate transport of additives for the contents of the container in a sterile and convenient manner that enables mixing according to a user's preferences before the opening of the container and dispensing. According to some aspects, the configurable package can include pre-perforated portions to facilitate or allow a user to controllably mix and/or dispense additives onto the contents of the container. In some embodiments, an adaptor can be used to incorporate the described cap with existing bag or rigid disposable containers.