Is there such a thing as stain proof fabric? Not really. However there are fabrics on the market with new technologies. Some of those fabrics ( offered by companies like Kravet, Duralee, Fabricut, etc) with Nano technology or so called krypton fabrics, actually repel water and other liquids.
I am currently working on a job at Blackberry Farm, where they requested a fabric that would repell liquids. We are using this fabric mainly for seat cushions on built-in dormers, for pillows, as well as around the dining room table banquette. Of course those fabrics also come in handy to upholster furniture.
Event though those fabrics are much more durable, the cost of these fabrics is not much higher than quality upholstery fabric.