Diet Coke
Diet Coke does not use a modified form of the Coca-Cola recipe, but instead an entirely different formula. The controversial New Coke, introduced in 1985, used a version of the Diet Coke recipe that contained high fructose corn syrup and had a slightly different balance of ingredients. In 2004, Coca-Cola introduced Coca-Cola C2, which it claims tastes much closer to Coca-Cola but contains half the carbohydrates. In 2005, the company introduced Coca-Cola Zero (replaced by "Coca-Cola Zero Sugar" in 2017), a sugar-free variation of regular Coca-Cola.
Pepsi
According to Consumer Reports, in the 1970s, the rivalry continued to heat up the market. Pepsi conducted blind taste tests in stores, in what was called the "Pepsi Challenge". These tests suggested that more consumers preferred the taste of Pepsi (which is believed to have more lemon oil, and less orange oil, and uses vanillin rather than vanilla) to Coke. The sales of Pepsi started to climb, and Pepsi kicked off the "Challenge" across the nation. This became known as the "Cola Wars".