I will keep it locked, roll the window down and let them know they can't bring the drinks. If they say, "Oh, no problem" and drink them or toss them immediately then I'll take them. ANY argument and I tell them they need to cancel and order again once they are done drinking up. Then I drive away. 90% will cancel.
I used to just tell them no and park duwn the road and collect the no show fee but we don't have that where I am.
I generally just tell folks with messy food they are eating to cancel, finish and call an uber. If I tell them no eating and they bring the food they almost always will try to eat it anyway. If it's bagged up and they are going home it can go in the back (I have a hatchback) but when they're already halfway through a taco or digging out fries it never ends well if I take them. At the least it's greasy fingerprints everywhere.