@Alex-and-Alex0 I hope you are well!
It is tricky, as different guests have different expectations, and different hosts do different things!
For my listings that are never owner-occupied, I leave the fridges totally empty, the freezer with fresh ice as @Sarah977 says.
If guests leave behind sealed items that would be useful to the next guests I will leave these in place after checking seals and dates, and talk to the guest about them in the home tour. If they don't wish to have them I take them home for myself- I hate food wastage.
For listings that I support where the owners are in residence when guests aren't staying, the owners items that won't perish during the guests stay, stay on a specific shelf in the fridge and I point this out to guests so that it's clear whose it is and what it's for- I would never expect a host to throw away their own, perfectly good food items so a guest could have a empty fridge for their stay.
Paul.