It would depend on your route.
Personally, I'd go up the F and then across to the Sault. Black Creek (who also have limited food options) for fuel and up to Aubrey Falls Trading Post for lunch (closed on Wednesdays). Both have Facebook pages for info and contact.
If you go south there are options in Iron Bridge and Thessalon. I don't believe there is anything near Wharncliffe any more.
Last time I was through Iron Bridge, I believe we ate at the Esso gas station/cafe but that was 10 years ago.