A bung-hit is when person A (receiver) seals their lips around persons B's (giver) anus. Then person A passes gas and person B inhales deeply and holds their breath.
Offering, or suggesting, that someone receive a bung-hit is considered to be a vulgar insult to many; and therein lies its value in communication.
In a sarcastic and obnoxious tone:
"Hey, why don't you plant your lips around my anus and I will fart and you inhale deeply. Have you ever had a bung-hit before?"