Originating from aforementioned Sprite commercial. However, in day-to-day use is actually a term for a cumshot splashing the back of the intended recipient's throat forcefully, in same thirstquenching manner as Sprite.
Chris exclaimed to Joe, "Last night I awoke to yer wife giving me favors under the covers. Yeah, you know she got that *SHPLADOW*! Then I promptly kicked her out the window & went back to sleep."