In 2025, Classic Coke captured 18.5 % of all carbonated soft‑drink sales in the United States, keeping it the market leader, while Pepsi accounted for 8.1 %. The rivalry intensified in 1975 when Pepsi launched the “Pepsi Challenge,” a blind‑taste campaign that claimed more people preferred Pepsi. The campaign was revived in 2025, and Pepsi Zero Sugar reportedly won 100 % of the sampled markets.

A 2004 Baylor College of Medicine study found brain scans suggested that seeing the Coke brand cue activated areas of the brain linked to memory and deliberate decision‑making, whereas the Pepsi cue did not produce a comparable effect. The researchers noted that the small sample size limited the conclusions, but the results point to branding and cultural associations influencing preferences before taste is even evaluated.

Together, the historic branding, the subtle ingredient tweaks, and the powerful cultural associations explain why many Americans stay loyal to either Coke or Pepsi, often independent of the actual taste.