I supply breakfast only for their first day, to save them shopping while still jetlagged. Per guest, I leave one mini cereal box, a small long-life milk, a small yoghurt, an apple, a small juice, a sachet of instant coffee, and either a muffin or a breakfast bar etc. It’s easier when I have a couple as I can use a larger milk and a two-pack of muffins. I used to leave fresh croissants or bread rolls, but I hate waste and I grew tired of coming in five days later to find it all wasted. All these things are sealed and won’t go bad if the guest opts not to use them. There’s also porridge oats and more coffee & tea in the cupboard, plus food other guests have left behind. I leave a welcome note propped up in the basket in the fridge asking them to enjoy these items as they’re for you, etc.
I don’t charge for breakfast or tick it in the amenities list, but it has been mentioned dozens of times favourably in my reviews and people are clearly very pleased. I had two complaints (because of course you should complain about items given to you for free, right?) one saying the breakfast was childish (rice and coco pops etc instead of muesli), and one saying the breakfast wasn’t good enough. I switched to only offering corn flakes and I now note in my listing that I leave light cereal for their first day, and it seems to have cured the complainers. 