The staff may be giving them a stash of clean drinking glasses to use. Plastic glasses are used to prevent injuries from dropped glasses by those who don’t have as sure a grip in their twilight years.
The patient may have dementia or Alzheimer’s. My mom used to stash all sorts of stuff in her clothing drawers. Empty cups, lids, napkins, lots of napkins, bottle tops, plastic rings, rubber bands, paper clips, etc., even fruit, what have you.