I started out as a "client" on rover and am now a sitter/walker. I always ask my self "what would I do as an owner in this situation" If I had someone coming to stay at my house I would offer them my food tell them to feel free to eat whatever and to use the kitchen. In the case of being a sitter I just take the lead of the owner. If they offer me to have some of their food then I go with that or if they don't mention food at all then I bring my own food.