Translation:I am hot. I want something cold to drink.
Perhaps it's related to the participles? I'm looking here and seeing construction similar.
Perhaps juoda > juo (stem) > juotava (passive present participle) > juotavaa (partitive case)
Wish we had tips for this one!
Yeah, "juotava" in this case is a participle, and "juotavaa" is the word in partitive. :) It means "a thing you can drink".
You could translate "juotava" as just "drinkable" too, because it can be used in phrases like "juotava jogurtti" - "a drinkable yoghurt" or "Se juoma on ihan juotavaa" - "That drink is quite drinkable", meaning that it doesn't taste good but you can tolerate the taste enough to drink it.
"Juotava" can also be used in sentences related to obligation and/or need, in which case it's more like a verb than and adjective.
"Sinun on juotava tuo kaikki" - "You have to drink all of that".
(Sinun on syötävä/tehtävä/siivottava/pestävä/mentävä... - You have to do X)
"I want to drink something cold": "Haluan juoda jotain kylmää".
"I want something cold to drink": Haluan jotain kylmää juotavaa".
In both Finnish and English, the meaning is extremely similar, but not completely, perfectly identical. In the first sentence, the subject of 'to drink' is required to be the same as the subject of 'want'. In the second sentence, the agent of 'to drink' is most often the same as 'want', but theoretically, I could be wanting something cold to drink, to give to a friend.
Some people would also argue that one sentence emphasizes 'to drink', and the other emphasizes 'something cold'.
Moreover, the grammar is certainly different between the two sentences. In the first, both English and Finnish use the active infinitive. In the second sentence, English uses a passive infinitive, while Finnish uses a passive participle in the partitive case.
All that said, it wouldn't surprise me if the makers of this course decided these sentences are close enough, and eventually added your version as an alternative.
My opinion - although in English we take it to mean the same - "I want something cold to drink" refers to the drink being cold, whereas "I want to drink something cold" could mean that you are cold when you have the drink. Think if you were saying "I want to drink something sitting down", that would refer to your status rather than the drink. The quirks of the English language.