So in Wanikani, the term 飲み放題 のみほうだい means “All you can drink.” When it says this, does it necessarily mean drinking alcoholic beverages, or can it be any kinda drink?
It would depend on the particular restaurant and what they offer. It’s not unusual for there to be different “tiers” where you can pay more or less money to have different drink options. But most places will include non-alcoholic beverages in all tiers if they have them at all.
Kind of like bottomless brunch and unlimited refills then?
The reality of 飲み放題 is that in most cases all of the orders for your group will be taken at the same time when the server decides to come to your room or area of the restaurant. So the server will come, collect all the glasses from the last round and ask for new orders. This effectively limits how much you can actually drink, because they usually won’t come back more often to just get one drink for one person.
I’ve never tried to push this, and for most people they end up drinking plenty anyway… but most places that offer 飲み放題 don’t give you direct access to the drinks. (not that you were implying this, just explaining more how it works)
At places like family restaurants and karaoke, it’s more likely that something called ドリンクバー will be on the menu. This is a publicly available fountain drink area where you can legitimately go as often as you please. It’s usually not called 飲み放題 even though it basically is.
Tangentially, I’ve visited a restaurant with an all-you-can-eat salads and sides bar (and drinks? I think drinks were involved), and I dunno whether it’s actually in the name of it, but the waitress definitely used the world 食べ放題 when describing it to me. I particularly remember that, because it was within a few weeks of when I learnt it on WaniKani for the first time.
This is how they get you on the “all you can eat” chicken wing places.
It’s pretty much assumed to be alcoholic beverages at restaurants in Japan. As another comment mentioned, at karaoke places or western-style fast food with fountain drinks they usually call it a “drink bar”
Sometimes the 飲み放題 part is limited to just some specific parts of the drink menu though, and you have to pay extra for things like Sake (生ビール is basically always included from my experience)