It says in Shulchan Aruch Orach Chaim Siman 174 Sif 7 that one doesn't make a bracha on water in the middle of a seudah (bread-based meal). Even if the person was thirsty from before the seudah (and didn't drink water then since it might hurt him (see there Shulchan Aruch and Mishnah Brurah Sif-Katan 31)) and drinks now in the middle of the seudah, still a bracha is not made. The reason he is drinking now is because of the pas (bread) and that exempts the bracha on the water.
In general if a person would drink before the seudah and wouldn't be concerned for what it says in Shulchan Aruch, and was in fact thirsty but for whatever reason didn't drink, do they make a bracha then in the middle of the seudah (since they are drinking in order to quench their thirst)?
What about in a situation where a person was in fact thirsty but was unable to drink (like Friday night before Kiddush.) In such a case they would have drunk and weren't worried about what it says in Shulchan Aruch. However they weren't able to drink yet since they didn't make kiddush. Does a bracha have to be made now on the water (or whatever drink it might be) that they are drinking in the middle of the seudah in order to quench their thirst (assuming they didn't drink any wine from the kiddush of course)?