I not only drink a lot of soda pop, I have drunk a lot of different brands of soda pop over the years. During this time, I have noticed something whenever I drink orange soda pop, no matter what brand it is sold under. Orange soda pop always seems to have little carbonization. Why is this? Lemon/lime soda, and grapefruit soda always seem to have been carbonized well, but orange soda always seem flat compared to its cousins.
Because that’s how much carbonation they put into orange soda. Not a satisfying answer, I know, but the amount of carbonation for various sodas varies. Ginger ale has the most; orange soda has the least. This is a decision by the bottler, and evidently people are used to the lesser amount of carbonization in orange soda.
Mountain Dew does not have a ton of carbonation as well, though more than Orange Pop.
I feel as though there used to be a brand of orange soda with more carbonation, but can’t remember what it might have been. Do different makers use different amounts, or is there an accepted ratio for a given standard flavor?
I dunno, I feel like the Sunkist I drink is extremely carbonated (it makes my toes curl if I suck down more than one swallow in a row–no jokes, please).
Sunkist is also the only caffeinated orange pop I’ve ever encountered. Maybe it’s a fizz outlier as well.
It’s also pop, not soda 
Yes!* That’s* why I liked orange soda as a kid but could never stand any other kind of soda. And yeah, I’ve never liked Sunkist; too fizzy.
What about from soda fountains? Usually there’s only one carbonator, and it gives the same water/CO2 concentration to every soda line.
Fanta is decently fizzy, but Orangina is barely carbonated at all.
But not the same water to syrup ratio. So all that has to be done is set the orange one to give less carbonated water, more syrup, and then have the syrup be watered down to compensate.
Bigno-bango.
Also, in my experience, orange soda is the one least likely to be offered at a soda fountain, and perhaps this is why? I mean…McD’s, BK, Wendy’s, and Taco Bell don’t regularly have it…I can’t recall ever seeing it at any of those, actually, though I admit I was never looking hard…but I can say for sure that none of the ones near me have it. I also know that neither the restaurant I work at, nor the one across the street from us, has it.
I agree with the high fizz Sunkist theory.
Nice theory, but that’s now how soda fountains work, either. They’ll have exactly one water line for each flavor (either carbonated or plain water), and one syrup line. The standard dispense ratio is 5:1. I guess that maybe the orange syrup supplier could water the syrup down so that they dispense, say, 2:1, making a flatter soda. If I were the owner, I’d not be very happy with that dispense ratio, though.
I’ve not noticed at home; I don’t go to those often enough, and when I do, it’s via the drive through, so I only order Coke instead of my preferred "please mix 1/3 orange with 2/3 Coke, please). Down here (where I do go out to lunch frequently), there’s orange all over the place (and so I get my preferred mix).
Doesn’t McDonald’s have their own brand of non-carbonated orange drink any more? I now remember that I used to quite like that.