" To stick (stick) your head out of" something is to put your head through some sort of opening, usually a window, but here Mandy is sticking her head out of a " sunroof" (sunroof).
“To stick(stick)your head out of” something就把头从某种口处出来, 通常窗户, 但这里Mandy把头从“天窗” (sunroof)里出来。