make them a huge bid and they will pick someone else
there are ways
I worked with a guy who owned some six flats.
He explained his M.O..
ALWAYS show the unit to all comers but explain that he had a a previous offer and they would be next on the list.
He did not care what color they were but no trash.
He said one time he thought he was being ‘reviewed’, called them after a few days and never heard from them.