@monochromacolor "日本人は晩御飯とよく牛乳を飲みますか。" is grammatically correct and sounds natural by itself. But I don't think Japanese people often drink milk with dinner, some might drink milk (or coffee with milk) with bread in the morning, though.
@nomadatlatl interesting, thank you! I figured that you all might not, it’s not the most common in the US outside from the big dairy-producing states, either. I always see them drinking flavored milk in manga though, in little boxes. Is that just a manga thing?
In my opinion, I don't think 晩御飯 is a childish word, but it sounds informal. I would say that word in conversation among my friends and family. 夕食 is a neutral or relatively formal word. I use it in conversations among adults, bosses, and older people than me.
@monochromacolor In the first place, I have to say I'm sorry for having overlooked a mistake. Your Japanese sample sentence "日本人は晩御飯とよく牛乳を飲みますか。" is not correct. It should be mentioned as "日本人は晩御飯によく牛乳を飲みますか。" I didn't proofread it enough, sorry. 🙇
Secondly, I'm not sure Japanese people drink flavored milk so much. That being said, there are quite a few types of it here, indeed.