Soft drinks can contribute to canker sores for several reasons:

High Acidity

Many soft drinks, especially colas and citrus-flavored sodas, contain citric acid or phosphoric acid, which can irritate the delicate lining of the mouth, making it more prone to sores.

Sugar Content

Soft drinks are high in sugar, which can feed harmful bacteria in the mouth. This may lead to an imbalance in oral flora, causing irritation or inflammation that triggers canker sores.

Artificial Sweeteners

Sugar-free soft drinks often contain artificial sweeteners like aspartame, which can irritate sensitive oral tissues in some individuals, leading to sores.

Dehydration

Soft drinks do not hydrate the body effectively and may contribute to dehydration, especially if consumed in place of water. A dry mouth is more susceptible to irritation and less capable of protecting against canker sores.