They bought the powder, mattress covers, etc. and I bought some non-toxic bedbug spray off Amazon that was rated highly and had it mailed to their unit. 

The interior and exterior paint jobs involved a few hundred bucks in paint and were sprayed in a day.

For instance, I had vaguely heard about a fire-retardant foam which insurance companies can spray on properties in the worst-case where a fire is nearby and approaching the property.

Spray surfaces with bleach to kill any surface mold on the concrete or floor joists.

Or something where odors can seep into the floor (or walls if the cat sprayed)?

If there is not egress just do a minor finish, by that I mean LVP the floor, sheetrock the walls, spray ceilings black, and add some lights.

In that time the property flooded during Harvey and with insurance I was able to upgrade everything I didn't do during the first remodel (repipe to pex, updated double pane windows, spray in insulation) and since have had it leased up to current.

Lived in it 2 years and in that time the property flooded during Harvey and with insurance I was able to upgrade everything I didn't do during the first remodel (repipe to pex, updated double pane windows, spray in insulation) and since have had it leased up to current.

I've never had a tenant cause a large amount of damage like spray painting all the walls or stealing all the appliances.I even had a tenant that left the apartment immaculate but left a big turd next to the front door and an obvious finger smear on the wall. 🤮 

Remove the doors, then sand the interior of the cabinets and give them a quick spray with paint to freshen them up.