If you can find a Bigger Mexican market in your area. They are likely to have a big selection of soda from Mexico, in glass bottles and only sugar sweetened.
Coke / Fanta are the most popular, but I see sprite, Dr. Pepper, Pepsi, etc... all the time.
Plus Jarittos is excellent if you like fruit flavors.
I have heard about Mexican Coke so it sounds promising if they have Dr pepper also. I'm lycky to have all sodas here in Sweden sugarsweetened but we don't have
Root beer and Dr pepper in glass bottles. and i would never load a 50's machine with plastic bottles
I havent think about mexican store so i will check if i can find a mexican import store store here. but i'm not positive.