When smoking ganja, especially when using something heavy hit-wise (such as a bong), you drink thick milkshake as to coat your throat and shield yourself from the burning heat - hence the term 'coat your throat'.
If you really want to go for a high-class smoking session, you should seriously coat your throat whilst doing so. Such is the way of the ganja elite.
by Spice Tropics August 2, 2013