If one is no longer feeling satiated from the meal he had, for which he can no longer recite Birkas Hamazon, would he still need to recite Al Hagefen or Borei Nefashos for what he drank during his meal, if his thirst is still quenched?
Although not a direct answer, we might be able to drive an answer from what the Shevet Halevi 7:27:1 says about a similar situation (he’s discussing eating fruit and drinking without a meal, see there for his discussion).
He brings the Pri Migadim that says that as long as one is still eating and drinking, the food he ate beforehand doesn’t start to digest. If so, if his thirst is still quenched then it’s still considered that he’s satiated from the food (being hungry isn’t a contradiction).
Another angle is that it’s not a practical matter but a halachic matter. As long as it’s part of the meal, we don’t count it as the food is being digested. In that case as well, if his thirst is still quenched, his meal is still considered as if he’s still full from it.
The Shevet Halevi seems to favor the first angle, which would help even if it’s outside of a meal, it would keep the original bracha alive. However, the second option only works for a meal.
Since the question only refers to drinking during a meal, it would seem according to all opinions, he could still Bentch, and so the question of borei nefashos wouldn’t come up.