How is Holy Water made?

Does it come in pre-labeled jugs, or is it straight out of the faucet w/ something added to it, or some type of "secret recipe"? Also, what is the reason Catholics have the little sink w/ holy water right inside the church doors to use before they go into the main church? What if they forget to sprinkle it on before they sit down? What is the purpose of this water anyway?? Seems to me that if a little sprinkle is good, a BIG sprinkle would be better, right? Is there any concern about sanitation in the little sink- from so many contaminated hands, and lastly, why doesn't everyone just drink it, instead of sprinkling it?