Why do i get excessive phlegm when or after drinking soda?

Normal: Soda stimulates secretions whirpi so u get more phlegm

Irritation: Your throat area is reacting to a component of the soda.

Bicarbonate (sodium bicarbonate): sodium bicarbonate may thicken saliva. Try using a lemon in your soda and see if it helps. If not then use club soda only. The sugar of a real soda pop makes your saliva thick also so maybe substitute with a diet. If nothing improves then go to tea or coffee.