A lot of the McDonald's around where I live are homeless hangouts where I've seen various stuff going on. Water cups used for soft drinks and some old cups being brought in. I remember one manager confronting someone attempting to refill a cup and saying that she knew he brought it in.
Yes the ones in Seattle were mostly homeless day shelters preCovid. Most went out of business over the last 10 years. The owners made more money selling to an apartment developer that was willing to pay them $20m an acre for their property. The ones that are still open are a magnet for drug dealing. I avoid at all costs. The Chipotle 1 block away is always clean and bright, pretty decent food, open for in person dining, and free from any riff raff.