I figured out this morning why my lacrimal glands tend to produce ample lubrication exactly the second right after I get a big drink of water. It is not how I thought (that the water somehow goes up through my head immediately and out my eyes). Instead, it's probably because of my pterygopalatine ganglion (a parasympathetic nerve, meaning it's in close proximity and close communication with its subject, the lacrimal glands). The pterygopalatine ganglion is connected right at the back of my face near the upper mandible back to the greater superficial petrosal nerve, which in turn is connected back to the maxillary nerve. The maxillary nerve transmits sensory fibers from the maxillary teeth and mouth out to these sister nerves. 

So, when I take a drink of water, Maxillary Nerve says (innervates) "Hey guys, there's cold wet stuff in here, probably WATER!" and Greater Petrosal Nerve says "Dude, Maxillary tells me there's water going in right NOW!" and Pterygopalatine Ganglion says "Thank GOD, because lacrimal's been hung over since all that beer was consumed last night! I'll tell him!" And boom, my eyes fill with delicious, refreshing lacrimal fluids. So cool.