While it’s sensible to assume that the Hogwarts School of Witchcraft and Wizardry isn’t serving Chardonnay to the students in the dining hall, the novels do mention several times that they are drinking pumpkin juice.
Do people really drink pumpkin juice, on a widespread enough basis that it would be made the standard drink with meals for a fictional private school? Even a magical one?
The Drafthouse makes a butterbeer and serves it whenever they do the Potter movies. It needs something; I’m not sure what. Oh – and I have had pumpkin coffee, which I thought would be utterly vile. It was given to me before I knew what it was. Tasted quite nice actually.
It certainly wouldn’t be a traditional thing rooted in ancient history, as pumpkins are fairly newly-introduced to these isles - they were unknown here until the discovery of the Americas, where they are native.
In the neck-o-the-woods where my father grew up (western Montana) “bug juice” = soy sauce. It was so labeled on the family bottle, replenished regularly from restaurant packets. Fortunately for tradition, my children now know it by that name.
Back to the topic at hand: assuming that one gets pumpkin juice from the flesh rather from the seeds, &c., it strikes me that you’re gonna have to press a whole heap o’ pumpkins to get any significant amount of it. Without a passel of house elves to do the grunt work, I doubt that it would be a worthwhile enterprise.
I’m reading Harry Potter in Bulgarian right now and butterbeer has been translated as “beer shake”.
(My guess for the translator’s reasoning is that the Bulgarian word for “buttter” also means ink and oil, and you can only tell from context what exactly you’re referring to, and here there pretty much IS no context. Still, beer shake?)