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.Older couple from California, I would stop and explain the law. Group of young guys, don't even bother, they will one star you for not breaking the law. In general if they are a group, locals, or young they're going to rate you low if you accept and won't let them drink. But there's no hard fast rule, if they seem at all entitled don't bother giving them a chance. I haven't had this occurring as often lately, probably only took one or two drivers canceling on them before they realized that if they wanted a ride they better finish the drinks first.
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.