posted 6 years ago
It's not easy!
Although I'm often lax when eating in public due to the incredible difficulty of being otherwise, my preferred mode of eating eschews animal products and added oils. That fundamentally means that most processed foods are off my menu -- which, I imagine, is where most preservatives are also found. I can speak to the incredible difficulty of finding a restaurant meal made from whole simple foods.
Salad bars usually work for me, but I hear rumors that they sometimes spray a sulphite over the cut greens to keep them looking better on the bar. I don't know if that's true.
I can usually eat at Asian/Chinese buffet restaurants. There's often plain steamed rice in a cooker; that shouldn't have preservatives in it. I find that fresh fruit from the dessert bar mixed with rice and a bit of hot sauce (it's often in a bottle, so you could read the ingredients, but I don't know if it has preservatives) makes a tasty tropical meal.
Subway sandwich shops are a good possibility. You'd have to be leery of condiments and any sandwich ingredient that might have been in a can or jar, but there ought to be a safe sandwich that could be specified.
My aunt and uncle are very elderly and they have a vacation scheme that lets them eat how they want every day. They go to one location per trip, and rent an AirBNB or VRBO or similar apartment with cooking facilities. And they tend to pick locations that are walking distance from some kind of nice urban market with a wide variety of fresh groceries to choose from. Then they shop and cook for themselves while they enjoy the location. You could do this -- although maybe with reduced satisfaction -- by choosing a vacation itinerary with hotel "suite" rooms that have minimal cooking facilities, located near basic food shopping locations. Then focus on whole foods and stuff from the produce aisle that is less likely to have preservatives. It would be a lot of advance research, but possible maybe.
When I am taking a long road trip (cross country or up the Alaska highway) I tend to start with a cooler of very fancy vegan sandwiches, made real dry and wrapped in heavy tinfoil (perfect combination of protection and slight breathability). I use a stout whole grain bread plus relatively "shelf-stable" things like olives, hummus, cheese (there's a vegan one I like, but if you eat dairy you can find something fancy that doesn't have random preservatives), sun dried tomatoes (read labels carefully!) and other strong flavorful things with a bit of oil content for richness but very little water moisture. Kept cool these will stay fresh and attractive for up to a week, and I don't really get tired of them. Which is a good thing, because finding edible roadside food tends to be a total disaster.
I hope there's something in here that's at least slightly helpful!