Husband was in coach while I got upgraded to BC last week - PHL-ATL - and tried to use one of my expired coupons (also SENT TO ME EXPIRED) and the FA grumpily scrutinized it, then tossed into on his tray table and said, "This is expired, but we accept debit or credit if you still want your wine."
He told her water would be just fine.
Probably an SWA-er.