Coca-Cola and Pepsi are changing how they make an ingredient in their drinks to avoid being legally obliged to put a cancer warning label on the bottle.
The new recipe for caramel colouring in the drinks has less 4-methylimidazole (4-MEI) - a chemical which California has added to its list of carcinogens.
The change to the recipe has already been introduced in California but will be rolled out across the US.
Coca-Cola says there is no health risk to justify the change.
Backgrounder (California) on 4-methylimidazole (4-MEI)
Backgrounder on the different production processes of caramel