Weird that they went out of the way to hide the 'root' in 'root beer' even after the joke played out. It's not like that's a brand like A&W (which I'm surprised they didn't just change to A&M or something).
why is root beer called juice?
A common slang loan word for any sweet drink (so not water, tea, coffee or alcohol) in Japan is "juice" (as opposed to just fruit juice).
I imagine most translators usually don't leave that as is since it doesn't work if you just do a direct translation