I personally have not noticed a acidic feeling before, but I also take medicine for acid reflux. I know it's this way for ingesting certain foods/candy, for example certain items from the "mint" family. Peppermint/Spearmint/etc upon normal ingestion can slow down the process of digestion and makes the stomach produce more acid to compensate. (At least it's what my doctor explained to me) I do not know if it the same for inhalation of these flavorings, though.