The object appears to be a simple, unassuming paper bag. However, the paper seems to remain intact and durable no matter how crinkled or wadded up it becomes. 

Once per long rest, the baggie may be opened to reveal a pristinely crafted sandwich, the nature being that which lies within the heart of the opener. They may then consume the sandwich themselves or give it to another. Eating the sandwich bestows the benefits of a Potion of Healing, gaining back (2d4+2) hit points.

After consuming the sandwich, the user has the option of rolling a d20. On a 20, they may discover that the baggie also contains a deli pickle, which upon consumption restores user back to maximum hit points. On a roll of 1, however, the bag is torn accidentally and is destroyed.