In the past I have found students pick up on fluster/disorganization very quickly & run with it. Really fast. Depending on the age group, its hard to get them back.

I remember being that evening/night student after work all day & now I'm an instructor for evening/night. Lecture for the first part & discussion, hands on, short videos for the second part did help with focus.  Also encouragement from previous instructors to eat light! LOL! Anything heavy just added to the "want to sleep" syndrome.