Whopper and features American cheese, crinkle-cut pickles, chopped onions, shredded lettuce and sliced tomatoes on beef patty with your choice of mustard, mayo or ketchup. It's a bit cheaper than the Whopper at $3.29 (or $2.79 without cheese).
As far as fast food burgers go Sonic's version is fairly unremarkable and pretty average which is not to say it won't suit your burger cravings, it's just very middling.
It tastes a lot like a Whopper except grilled and you get your choice of mustard, mayo, or ketchup (or all of the above or any combination of the three) by default rather than having to request it. Plus there's cheese which is actually a little better than the standard fast food American with a bit of creaminess that melts properly.
Footlong Coney (that I can't finish because it's a long ass hot dog and enough for two people) which besides tasting better, is a frontrunner among fast food chili dogs rather than just middle of the pack.
Sonic Restaurant Locator
Nutritional Info - Sonic Cheeseburger (265g)
Calories - 630 (from Fat - 280)
Fat - 31g (Saturated Fat - 12g)
Sodium - 1140mg
Carbs - 60g (Sugar - 15g)
Protein - 29g