Central Texas here.
Whataburger is a local chain, fairly solid and well run. The burgers are decent, back in the day they use to grill the meat fresh, good stuff. Now you get good value for what you pay, always filling, menu is standard fare, but they do offer seasonal burgers which are really good. A good breakfast menu as well. Local secret, their burgers and fries can be microwaved, and will strangely taste better... no idea why... can't do that with other chains.
Sonic is also a solid choice, large menu, known for their cheap slushies and footlongs.
Culver's an out-of-state import, has a small footprint, well run, large menu, made fresh, very good. Known for their custard.
Usual national chains, quality dependent on local ownership. Hit and miss. Nothing to add.
Not a burger...
If you get a chance grab some Bill Miller's BBQ if pass through, best fast food bbq you'll ever taste. Also, good menu choices for a fast food joint.
Chick-fil-A... they will rule the World one day. Best to get on board now.