Don't listen to the person typing in 96-font, they are clearly insane. No one is getting 1099s for a half of a Panera sandwich and a cup of iced tea.
Honest mistake, just shoot your dm or compliance/expense dept. an email so it's on record. These lunch-type expenses will appear on providers' Sunshine report, so if it's someone who is adamant about not accepting meals they might dispute it. I have very few like this ( but do have a few and completely understand their perspective) bc they realize you are feeding their staff and are generally appreciative of that.