I don't know about some of your experiences at Sonic, I've been to Sonics in 6 states with no problem. The one 3 blocks from my house is great! And that's 40 years experience munchin' burgers!
In the "old" days, Sonic had #1 Sonic Burger: mayo
#2 Sonic Burger: mustard
My fav: mustard.
I will agree that Whattaburger is awesome, there are 2 in Arkansas, and they need MORE.
Backyard Burgers is ok, but pretty pricey considering what you get.
I make my own burgers. For the 4th, I made garlic stuffed burgers.
Personal Fav: Burgers stuffed with shallots, sauteed mushroom bits and Blue & provelone cheese...with stuffed cheddar & pepperjack jalepenos on the side...all done over the coals in my Weber.
68ROX