Cookout. LOL. They're average at best.
Bojangles for breakfast. They're pretty good. They've got sweet tea down.
Can't really recommend much in Knoxville that's right off the highway. There's a hole in the wall place called Victor's Tacos that's on UT's campus. They make good tacos (more So-Cal - but good). Culver's has good burgers (local chain). There's a local place called Double Dogs that has burgers, hot dogs, etc that is pretty good.
Knoxville has a pretty bad food scene. When someone here recommends an "authentic" Mexican place, I know that the salsa will taste like tomato paste and the queso will be cheddar cheese from a can.
We went to a food truck area park recently - and this is what "passed" for a steak burrito. Meat had zero spice - tasted like they boiled it. Rice was mushed together - looked and tasted more like polenta - but not even that good. I spit it out.