The main ingredients in Diet Coke are carbonated water, caramel color and aspartame. The beverage also contains phosphoric acid, potassium benzoate, natural flavors, citric acid and caffeine.
Carbonated water is water with carbon dioxide added to produce a fizz. Caramel color is made by heating sugar until it turns the desired shade of brown. Aspartame, an artificial sweetener made from amino acids, is used to lower the amount of calories in the beverage.
Citric acid is found naturally in citrus fruits and can also be manufactured from plant sources. Both citrus acid and phosphoric acid add acidity or tartness. Potassium benzoate, an antimicrobial food additive, is included as a preservative to prohibit the growth of mold or fungi. Natural flavors are essential oils or extracts from plants. Caffeine is a stimulant which can be manufactured or derived from many plant sources.