Not like in Europe, tap water is free of charge at any restaurants, diners, taverns or bars.
Therefore it is very rare to see a person ordering soft drink for lunch.
Even if you have a dinner at diners, ordering a drink is not a compulsory.
Then, variation of soft drinks at restaurants is not as same as in Europe. May be the restaurants would have just 3-4 types of soft drinks and usually juice is not available. Although juice is not available, Japanese thinks any beverage containing juice of a fruit is a juice. Therefore many people think that Fanta Orange is a juice.
The photo is a root beer which I ordered at Okinawan restaurant in Osaka.
Due to Okinawa was under administration of US till middle of 70s and still many military bases are located in Okinawa, American influence is still high.
Therefore do not expect to drink root beer outside of Okinawan restaurant in Honshu!