I often head to grocery store and make my own salad at or less than $4. I have the bottle of dressing at the office so can skip that weight of that. Best part is having exactly what I want on it in quantities I want. This store also has hot deli so I could get panini or fried chicken less than elsewhere and also has an eat-in section.
Extra bonus that I can pick up dog food or coffee or whatever on same stop. One grocery store easy walk from office but I don't like their toppings as well and their soup is not as good so I drive the 3 miles to the one I like.
I do occasionally go to Subway (walkable, same place as near grocery), usually with buy one/get one and save #2 for dinner. I always get a pile of veggies as I agree there is not much meat. I do like the bread, however.
We have a lot of food choices near our office, but the Kroger is the furthest option. Though I have at times gone there and got the salad bar. I don't consider the much closer Whole Foods an option. Their salad bar is double the price of Kroger.
If I find myself going for fast food, I tend to go to places with $2 options. I like the fish and fries basket at Long John Silvers for only $1.99. Then I fill out the survey on the receipt and get a free fish and fry when I buy a large drink that costs me $1.92 with tax. If I ever get KFC, I do their survey and get a free Go Cup on my next visit. These options work out better calorie wise and are actually pretty filling for a lunch. Subway is close by too and I go there when I have some $3 6" coupons or they are offering their $2 Customer Appreciation promotions (that they haven't had in a while). I still haven't gone for McDonald's 2 for $2 offer yet.
Subway sometimes has coupons in our area where you buy three 12" subs for $15. I end up eating 6" for dinner and saving the other two 6" pieces for the next two lunches. Wife is the one eating the other half of that deal. It is good that we like the same subs. I won't go to Subway if I have to pay full price. Their subs are not worth full price.
I find myself most days packing my lunch. I have started making my own soups at home and can usually come in under $1 for a lunch. If I take a prepared frozen meal, those are usually around $2-$2.50. I try to avoid that if I can now though.
I pretty much always avoid fast casual places like Five Guys or Chipotle. I certainly don't want to be spending $8-$12 for a lunch.