My partner falls asleep in every session; which alert technique should he use?

My spouse can put herself to sleep midway through whichever guided session, no matter what the time of day it is, even when she sits up in a chair. I fear they are not enjoying the mental rejuvenation, but the physical refreshment. His name is Jatin, DOB is 1st January 1990, 3:44 AM. I would have to discover a method that would keep the mind alert and active, such as a walking practice, but without causing them to feel even more exhausted.