Most visitors to this site relax, watch TV or take a walk when they get tired of learning. Various forms of relaxation predominate among nearly half of those taking part in the poll. To prevent erasing old memories for the sake of storing new one's, the brain fights against new learning by making us tired or drowsy. Some people claim they do not get tired of learning. Drinking coffee or caffeine beverages may not be a good idea for efficient learning.
Caffeine can be helpful in dispelling sleep inertia upon arising.
However, it is a poor substitute for mental rest and sleep. It will also mask the overload effect which may ultimately be harmful for learning. Probably this is why it ranked lower. No wonder, snacks are not popular in overcoming learning-related tiredness. Take a break.