What function does "for us to drink together" have here?

Hello my friends.

The original sentence is "I've brought some coffee for us to drink together".

Could you please tell me what function "for us to drink together" has in the sentence?

Is this an adverbial phrase giving a purpose or an infinitive phrase(adjectival) referring to "some coffee"?

Or I can ask which reading would be correct?

1-) [I've brought some coffee] (why I brought? Because -->) [for us to drink together]

or

2-) I've brought [some coffee for us to drink together](Adjectival)

Thank you for help. (My opinion is that it functions as an infinitive phrase(adjectival) here.)