Sit there and dig through your to-go bag - This is bad for several reasons: it’s rude, since you’re assuming they screwed up your order; You’re holding up all the cars behind you; The worker is being timed on how fast they move cars past the window and this is slowing that down.
Say: "You messed up my order" - The person you’re dealing with at the window didn’t make your food, so they didn’t mess up your order. They’ll happily fix it for you, but they put your order into the computer just as you ordered it and they didn’t add the mayo to your McChicken sandwich.
Bang on the window to get my attention - Talk about rude! If you’re still sitting there after the worker gives you your food, they’ll come check on why, no need to bang on the window.
Try to give me garbage to throw away - It would be a health code violation to bring your trash into their restaurant. And who knows what you’ve got in that nasty napkin!
Ask for a refill - They can only do refills inside the restaurant for the same reason they can’t take your trash - who knows what you did with that cup after they gave it to you.
Talk really quietly - It’s super loud inside McDonald’s, so speak up and save everyone time.
Ask "can I have a straw?" when I literally just said, "straws and napkins are in the bag, have a nice day!" - Pay attention and listen up, folks.