An acquaintance of mine was a chemist, whose job consisted of discovering the components in items sent to his lab - often times food. Unfortunately, he loved sharing these stories with people around him. One reason he didn't get invited out to eat very often...
We'll sometimes stop at a fast food place when we're driving with a destination in mind and a tight schedule. Normally we pack out our travel food in a cooler. Often times it's not the ingredients that cause problems, although anything with a sauce is a no-no in my book, but the method of preparation and what they use in the prepararation. But that goes for any place. Was at a home cooked meal place yesterday, and an couldn't figure out why their website advised one prepared egg (sunny side up) was 145 calories, when an egg alone has about 70. A little research revealed it was the buttery/oil they cooked it in.
Not a McDonalds fan used to love Wendy's, but they've changed over the years. There's something about a grilled Burger King hamburger, though. They use an open flame grill - not greasy.
Chipotle's is an excellent fast food option, IMO. A huge burrito about five bucks, and you select the components.
We generally eat very healthily, snacking on fruits, nuts, hummus, but that can also be more expensive.