What new substances were formed in the alka seltzer and coke experiment?

In the Alka-Seltzer and Coke experiment, the primary new substances formed are carbon dioxide gas and sodium citrate. When Alka-Seltzer, which contains citric acid and sodium bicarbonate, is added to Coke (which is acidic due to carbonic acid and phosphoric acid), a chemical reaction occurs. This reaction produces carbon dioxide gas, which creates the fizzing and bubbling effect, and forms sodium citrate as a result of the neutralization of the acids.