the term you're looking for is "ghosting". its a very grey area between sweating someone to help them/to coach them and sweating them to help them play better.
in my eyes, if you're discussing thought processes (i.e. did you think about doing this/i think this other line is more profitable) after the hand has occurred then it's fine. however, if during a sweat someone is deep in a tournament and just asking a more experienced player what to do each hand, that's ghosting and unethical
of course, there are plenty of players out there, as i've read about on 2p2 and seen first hand with different styles of play, who have no qualms about ghosting players who are deep in big tournaments