lol! Actually, we don't have a cat either! We have two small dogs but we live on the third floor of a condo. We have a huge balcony, so we've taught the dogs to go pee in a kitty litter box in the morning so we don't have to rush to get dressed and take them out....ALWAYS THINKIN HERE!
I knew a guy who would buy a flat of turf which he kept on a tray on his apartment balcony. His dog used the little patch of grass to do his job. He (the guy, not the dog) would replace the flat once a month.