Burger King stopped publishing ingredient statements in 2019, so this is rated on its own May 2018 nutrition PDF and 2017 allergen PDF, which confirm a corn/canola/soy/cottonseed fryer, soybean-oil buns and an interesterified-and-hydrogenated-soybean-oil tortilla. 31 of 71 items name a seed oil and 56 of 71 carry an additive, but everything here is 7 years old, which is itself the finding.
Burger King has effectively stopped disclosing ingredients. The last statement-bearing document is its own May 2018 Nutrition Information PDF and its Nutritionix ingredient widget is live but empty, so this is rated on that PDF (71 statements) plus the June 2017 allergen PDF, which states verbatim "Our fryer oil contains: corn, canola, soy and/or cottonseed oils." The beef is clean ("100% USDA inspected Ground Beef") but no sandwich escapes: buns carry soybean oil, the tortilla is "Vegetable Shortening (Interesterified Soybean Oil, Hydrogenated Soybean Oil)", and mayo, tartar and Stacker sauce all begin with soybean oil. 31 of 71 items name a seed oil; the 40 that don't are mostly sodas, syrups, jams and cheese. 56 of 71 carry an additive: HFCS 21, modified starch 19, mono-and-diglycerides 18, artificial flavor 17. Dyes are in 3 items (Pickles, Strawberry Shake Syrup, Froot Loops Topping) and BHT only in Froot Loops Topping. Confidence lowered because the data is 7 years stale.