"Do you want something more to drink?"
Translation:Haluatko lisää juotavaa?
Enemmän is "more" as in "more than." You use it when comparing two different quanities. Lisä is "more" as in "some more." You use it to indicate an additional quantity of something (and, in this example, it's in the partitive).
I'm a learner, not a native speaker, so you would do well to wait for a more authoritative voice to comment before you commit my explanation to memory :-).
I put "haluatko joitain viela juoda" and was marked wrong. When I saw the Duo correct answer, I wondered what the extent was of mess I'd made of my effort, and put it into Google Translate to find out ... and, lo and behold, it came back as "do you want something more to drink". Could anyone from Duo care to comment, please?
I think (although I am a learner too), that google translates sentences word by word, and than ofcourse it guesses right. In real life people would understand what you meant to say, (I noticed that, since I tried some of my new learned Finnish in Finland last week and I made a lot of mistakes) but it is grammatically incorrect.