I do not think that in the American english translation you would need to add an "a" even at a social gathering. I could be wrong though, but I do think that if I were proficient in spanish and was translating to english I would translate it as "does he want a tea." Also when tea, coffee or whatever is offered to an individual, as opposed to a group, I am not sure that more than one cup is ever implied. Therefore it does not seem that the offer would need to be clarified by the word "a".
Not in Texas. Youll catch me ( and others) saying this multiple times a day. And even if it's not common, its definitely not grammatically incorrect.
At the end of the day, you have to remember that Duolingo is trying to teach us Spanish, not English. As a result, sometimes they have to tweak the english translation, so that you can understand the grammar and semantics of the Spanish you're learning.
I agree with you on every point, however, the implication here is that this is how everyone in Spain speaks.
It subtly implies that if you don't say "un" before té or café that people won't understand you (or that you'll sound like an idiot).
Ultimately, the question to me is: Is "¿Quieres café?" Grammatically correct Spanish?
Because unless I'm a barista or waiter (or maybe in the drive through ordering for you), I don't think I'll be specifying whether you want "A" coffee or not when I ask you.
Its not that strange actually! It just depends on the context! People in Maine use it all the time. If I was making tea and asked someone if they wanted any, I might say "do you want some tea" because im implying that I have one big container of tea and am asking if you would like "some" or a portion of the mass, but if I were to have, lets say, cans of Arizona tea, for example, i might hold it up, point at it and ask "hey man do you want a tea?" And this would make sense without question. Just like, "do you want a pepsi" or "do you want a banana." This being said however, I think that if I had a giant 5 gallon jug of Gatorade, and then asked someone "hey do you want a cup of Gatorade" this would make more sense than "hey do you want a Gatorade" in this situation, because of the individuality of a cup or bottle, vs the massive amount of liquid in a 5 gallon jug. You could either want "some" vs "a or an" when you say "I want a bottle of Gatorade" you're implying you want the thing as a whole. you would say "a cup, a bottle etc. But when there is mass that you only want some of you say "some Gatorade, some coffee", etc. This being said however I still think you could get away with saying "do you want a Gatorade" in the context of there being a 5 gallon jug of the stuff. Although it might sound just a bit off, but not many people would really notice, and if they did they probably wouldn't try to correct you.
So now can we say do you want some tea or do you want a tea ? I think the correct one(just my opinion is..)do you want a cup of tea and also the same thing for water and any drinks ,you say :do you want a glass of water , do you want a glass of milk ..etc..and finally guys it is just an opinion but I wonder if we can use "a" instead of "some" (what do you think ?any native American speakers can know???)
My main difficulty is understanding the spoken Spanish. Aside from the fact that many syllables are elided, the emphasis differs from what I would expect. E.g , with the "un té," the empahsis is on the "un." With "a tea," I would put the emphasis on "tea ". Emphasising the "a" would be stressing the idea that they only wanted one seving.