honestly? i have been THISFREAKINGCLOSE to falling asleep a (couple)times or two. i am a last semester nursing student and they often put me as a 1:3 patient sitter in our "crazy room" ( our only multiple room that houses the confused elderly, combative, etoh/drug withdrawl, suicidals etc)
well, when the shift starts at 6am and its still dark out and all the patients are (actually!!!) sleeping, its pretty easy. or if its 230pm and they are taking a post lunch snooze, its hard not to feel tired yourself. that said, i try to open the blinds/turn on the central light (never the overhead one, im not that mean!) about 15 mins before breakfast so i can get THEM used to being up when they "should be". If i am feeling particularly sleepy, i make sure i get up and walk around (ahem, pace really) the room, get myself some ice water and coffee asap.
for me, the worst thing to do when i am feeling sleepy is to sit in the room in the dark in the comfy chair.