I gave a girl a trial lesson. about half way through she said she felt ill. I passed her the sick bag she filled it and the second one.
Undeterred, she decided to continue and is now in the solo cross country stage and never an airsickness symptom again.
I once had occasion where a students flying made ME feel sick. The remedy was to ask him to let go of the controls and as the aircraft flew on smoothly now nicely trimmed out everything settled down.
A valuable lesson learnt about overcontrolling.