The top four finishers were:
Arby’s Tangy BBQ Sauce. It’s a cheap, middle-of-the-road bottled barbecue sauce, perfect on fries.
Church’s Chicken Honey BBQ Sauce. You can taste the chile powder and honey.
Shake Shack BBQ Sauce. It’s zing of mustard is pronounced, especially alongside the others. Admittedly, I’ve always liked a bit of mustard in my ketchup for fries.
Wendy’s BBQ Sauce. The massive amounts of sugar and molasses, along with a strong flavor of liquid smoke (which I would find appalling on actual barbecue) were a perfect pairing for the salty, fatty fries. It also contained the highest number of spices, at least those divulged on the labels.

