*Spoiler alert: If you are squeamish about menstruation, please do not read the following.
Ladies of a certain reproductive stage know that surviving an apocalypse (or, for that matter, enjoying a vacation/long hike on a deserted tropical island) presents one significant additional challenge not encountered by our male counterparts: the "period".
When the supply of non-sustainable feminine hygiene products will most certainly be the first thing to be pillaged from burning CVSs world-wide (OK, maybe after smoked beef-jerky), how are we ladies to handle daily life, work, escaping an alien invasion, etc?
Yet this is the same question that women all over the world are asking themselves right now, perhaps excepting the aliens bit. In some places, women cannot work or go to school during that time of the month, severely impacting their ability to live their lives.
Those of us privileged enough to live in a place with limitless tampons can still benefit from the cup. (There are multiple brands.)
Why the cup?
1. Much safer than the one-use alternatives.
2. Pays for itself in one month.
3. Completely unnoticeable to the user (and everyone else).
4. FANTASTIC for the environment. No waste/reusable.
5. While it sometimes takes a couple of cycles to get over the ickiness and learn how to properly use the simple device, once that is over, you can survive the apocalypse -- no problem.