Hawaii - Hawaiian Sun
While this isn't technically a carbonated soft drink, it's one of Hawaii's most popular-selling beverages. If you ask any Hawaiian what their drink of choice is, they're going to say the Pass-O-Guava flavor. No one does it better than Hawaiian Sun.
Idaho - Iron Port
While Iron Port isn't one specific drink, it is a brand that stocks several soda fountains. Iron Port is similar in taste to root beer, but with a spicier flavor. You can find Iron Port in nearly any restaurant in Idaho.