Bunless sandwiches work just about anywhere.
Arby's sliced meats and chicken are good. Subway will make any sub a salad. Cesear dressing IS different brand by brand, but ranch, bluecheese and oil/vinegar are typically safe. I checked with my pizza joint and they don't put sugar in the sauce=so I eat toppings over salad greens. Bruchi's cheese steaks over a spinach salad is excellent! Sit down/breakfast places are a lot easier. Good luck to him!