There's tons of food to eat! Just stick to real food: not processed, packaged, shortcuts. Salad bars haven't had sulfites for many years, but ALL processed potatoes, including the dry boxed ones, are allowed to have it to keep the product white. Any method of keeping out oxygen will do, but sulfite is cheap.
First make sure sulfite is your problem. Keep a food log. Write down everything you eat and whether you have a reaction an hour or two hours later. Then "challenge" test each food item in the suspect meals. You can start with a tablespoon of things like potatoes, but maybe a teaspoon of avocado dip or other suspect foods. Then twenty minutes later eat two T or t. Another twenty minutes and 4, then 8, then 16. Stop if you have a reaction!!!
When you have your list of trigger foods look on the various lists: sulfite food allergies, MSG, GERD ... I'm not saying everyone with GERD is allergic to sulfites! But food triggers are well known to us patients even if not to many doctors. It's also probably that a lot of people have more than one intolerance. I have a severe "true" allergy to sunflower seeds, and I don't tolerate milk well.
Restaurants: If you have food triggers, just avoid those foods. I can't eat anything in Olive Garden. Garlic is naturally a source of sulfite! I do quite well in Wendy's. I just avoid french fries and opt for the baked potato. I am less afraid of a little plain salmon with maybe some mercury causing cancer in twenty years than something like barbecued ribs(pork, brown sugar) that I know will give me reflux and tachycardia before I get to the parking lot.
Bread is a real problem. If a food place makes their own dough, it might be free of sulfite. But most places, including grocery stores with bakeries, are lazy and bring in the dough frozen. Then it's most likely got sulfite as a dough conditioner. Pizza dough is generally on sulfite allergy lists. I find if I avoid sulfited products I can tolerate a single slice of pizza once a month. But that's an individual tolerance!
Cheeses are all different too. I avoid the really tasty hard cheeses, or eat only what can go on a single cracker. And not every day!
Tomatoes are great raw, but cooked into sauce they generally have vinegar, cheap sugar, etc, which are sulfited.
If we all check to see if we have at least a few trigger foods, we might reduce our symptoms even if we don't find a cure.