Although i do think there is more money to be made in RE than selling soap. 

I used to leave a bottle of decent champagne when a guest mentioned they were visiting for a special occasion like an anniversary or something.

Just the basics, little shampoo, conditioner, soap and lotion bottles in each bathroom, salt, pepper, cooking spray, coffee grounds, etc..

We had our 1 year anniversary two months ago in a little over a year that we have been at this we have grown our portfolio to a value of 290k we will wholesale one of the properties and the rest will generate monthly rent / Mortgage payments to $3,670.  

NEW TENANT GIFTSHere's what we give new tenants.....Cleaning Bucket with Cleaning Supplies:white vinegar, baking soda, awesome degreaser, disinfectant wipes, carpet spot cleaner, magic eraser, all purpose cleaner, scrub sponge.Tote Bag with Useful Items and Tools:hand soap, paper towels, plastic garbage bags, toilet paper, toilet plunger, Zip-It (strip for clearing hair clogs from drains), plastic clothes hangers (6), shower curtain liner (good quality cloth one), laundry detergent, dish soap/dish detergent, cutting board, "Freeze the Grease, Save the Drain" kit, “Recycle” bag for collecting materials for recyling, magnet with our name and contact information, picture hangers.Refreshments In the Fridge (for move-in day): several bottles of water, healthy snacks, bottle of sparking cider with a welcome note attached.Larger items: Welcome mat, shoe tray.

Does anyone follow up shortly before the anniversary of the guest visit such as 9 or 10 months?  

Laundry Machine soap, Dryer sheets, Bar of Soap, Shampoo, toothpaste, etc.

One small oil spill-yes if they didn't notice it was leaking and then got it fixed; but multiple spills means they didn't fix the car.Options to try are baking soda and vinegar or dish soap like dawn that breaks down the oil. 

Like Michael said, I would use a cleaner once a month to clean or biweekly, restock the common area items (like TP, dish soap, etc), and sign up for routine lawn and snow services.

We played with the idea of a Laundry vending for soaps and dryer sheets.