If i’m in the airport with someone who is flying business class may they, after taking a sip from a can of soda in the lounge (since they have free drinks), bring out the rest for me? Would this apply even if they only took the drink because they knew I wanted the rest?
If somebody takes the drink for himself, he can give the rest to you. Yet, it would not be permitted for somebody flying business to take drinks with the sole intention of giving it to you. His having a sip on the way would not render this permitted.
Rema (Even Ha’ezer 28:17) discusses the question of a guest who takes his food, and uses it to wed a bride. According to Rema, the kiddushin is valid, meaning that the food belongs to the guest, and he can do with it as he pleases.
Others show that according to Rashba (Bava Metzia 88a) does not concur, maintaining that the food does not belong to the guest, and this is discussed at length with regard to fulfilling the mitzvah of matzah, and other similar matters (see Sefas Emes, Succah 35a; Imrei Binah Pesach 23; Kovetz Shemuos (Rav Elchanan Wasserman) Bava Metzia 24; Kehilos Yaakov Bava Metzia 48.
However, this applies specifically to that which the guest is given by the baal habayis. In this case, the baal habayis is the lounge operator or airport authority, and the question is which food does he give his guests. It stands to reason that the food and drink offered in a business class lounge is meant for business class travellers only, and he “gives his guests” no more than they wish for themselves. Therefore, it would not be permitted to take food and drink for the sole purpose of giving it to others.
Note, however, that the attendants in the lounge are authorized to answer such questions, and if they give permission, one can rely on this for taking the food or drink.