Some people who have little respect for their brain cells or kidneys drink the stuff in order to get high on the dextromethorphan (aka DXM).

This is a really bad idea. DXM is a dissociative (or deliriant) and generally scary stuff. Cough syrup also has a lot of sugar, which hurts your kidneys and pancreas. It also often has acetaminophen, on which you can OD, or guaifenesin, which makes you puke.