If it is hot out (like every day in the summer) repeated stall practice can cause airsickness/heat exhaustion. Most light airplanes rely on ram air for the air vents and since stall practice usually occurs at low airspeeds, you have less ram air. Students who get hot do get airsick more often that others. Passengers also tend to get sick in these conditions.
As for steep turns, I had a couple of students who felt queasy after several steep turns on very hot days. If able, you might try to climb a couple thousand feet higher (like 5k or 6k) to do maneuvers as the air is cooler there.