I have used food to deter cats from toileting in the wrong place, I'm not sure dogs are as fussy. I feed mine on (clean) pee pads, they still know they are toilets when not being used as tablecloths. I couldn't leave any food laying around though, it would be eaten instantly. Is a food reward even going to work as reinforcement with a dog who isn't very food motivated?
For most dogs being allowed to pee indoors and not have to endure the nasty weather is reward in itself, which is why toilet training is so tricky in winter, indoor accidents are self-reinforcing.