A brief period of sleep of around 15 to 20 minutes, preceded by consuming a caffeinated drink or another stimulant, may combat daytime drowsiness more effectively than napping or drinking coffee alone.    A stimulant nap (or coffee nap, caffeine nap, occasionally napuccino)  was discovered by British researchers, Horne and Reyner, to be more effective than regular naps in improving post-nap alertness and cognitive functioning.   In a driving simulator and a series of studies, Horne and Reyner investigated the effects of cold air, radio, a break with no nap, a nap, caffeine pill vs. placebo and a short nap preceded by caffeine on mildly sleep-deprived subjects. A nap with caffeine was by far the most effective in reducing driving accidents and subjective sleepiness as it helps the body get rid of the sleep-inducing chemical compound adenosine .  Caffeine in coffee takes up to half an hour to have an alerting effect, hence "a short (<15min) nap will not be compromised if it is taken immediately after the coffee."    One account suggested that it was like a "double shot of energy" from the stimulating boost from caffeine plus better alertness from napping.  This procedure has been studied on sleep-deprived humans given the task of driving a motor vehicle afterwards,  although it has not been studied on elderly populations. 
Imagine you're a predator out hunting for food (and Jesse Ventura), but all the regular animals you would eat are nowhere to be found. You spend the entire day looking for food and find nothing. About 16 hours later your brain starts freaking out. It knows that if you can't find food, the jig will most certainly be up. So at this point, your brain doesn't give a tinkerer's damn about sunlight and sleep cycles -- it just wants you to find something to eat, and fast . You stay up well into the night and eventually find some nocturnal prey, devouring it desperately. Your brain (through the food-clock) makes a note of this time and declares it to be your new biological morning.