My property has a vacancy problem because of the area, so we have held several Customer Appreciation Days and/or weeks...
We've done a simple "drive thru" breakfast where we had single serving OJ, milk, choc milk, coffee, etc and had donuts, muffins, bagels and the fixing...They could drive up to the office, one of the staff ran out with a menu, got their order and then we brown bagged it for them...inside each bag we had a "Thank You for being a wonderful resident" card...
We've had a cookout with door prizes given away each half hour
We've had pizza parties...with lots of games (for the kids)
We've had balloons blown up where each balloon had a note that gave them a small gift...gift certs to grocery stores/gas cards, etc. and a few of the balloons had notes for larger gifts..one resident got their rent free for one month, etc.
We've sent out notes that just said "thank you for being a wonderful resident"
My residents just love a reason to get together, so they don't really care what we do...
Hope that helps...