Free toothbrushes, floss, and toothpaste from your dentist. 

You can also leave out some bulk hotel toothbrush/toothpastes, make up removers, earplugs, sleeping masks, etc. if you really want to step up a "In Case You Forgot" basket.You can keep a closet with extra of things that has a lock on it and if someone is irrate because they don't have enough pods, you can at least have a back up solution for them if you choose too. 

Quote from @Collin Hays: I've been working on an invention over the winter - an all-in-one toilet paper and toothbrush.

Quote from @Jonathan Greene: Quote from @James Hamling: Thing is @Jonathan Greene, your message, as true as it may be, comes across to a whole generation like that of the person giving away apples and tooth brushes for Halloween..... 

I heard about a great system for improving my dental health, which requires purchasing a second toothbrush, a Sonicare, for minutes 3 and 4.I go to the dentist, and she tells me how great my teeth are doing.

Does providing complementally k-cups/teas, popcorn, spices, toiletry essentials (toothbrushes, floss, bath wash, shampoo, conditioner, soap, paper products, makeup remover, laundry detergent, firewood with firestarters for the fireplace and firepit constitute as substantial services?

Vacuum out the gap first... sometimes use a toothbrush to make sure there isn't dirt in there that will prevent clicking together. 

I’ve given food to hungry people, I’ve given the shirt off my back to an old naked woman, I've bought shoes for kids, built a school for aboriginal tribal families in the mountains, and handed out toothbrushes.  

I do some popcorn, Rice Krispies, sleeping masks, ear plugs, toothbrush /toothpaste, etc. local partnerships: find restaurants you may be able to get a discount for sending guests over for.

If your hoping for repeat guests (where they pay full rate and you don’t have to share it with Airbnb or VRBO), then provide hotel size shampoo, conditioner, body wash, small toothbrush and small tube of tooth paste.