I'm not sure why everybody's tip-toeing around the obvious.
There should be an IN-N-OUT attraction/restaurant in DCA.
You begin by climbing into a stylish convertible. Trackless? Wire guided? Busbar? Worlds Fair WedWay - probably not? For full immersion, you could then wait an insufferable amount of time, but that might be skipped (upcharge?) and you proceed straight to the menu board, where your order is taken. Then, due to the stop and go nature of a drive-thru, you pause at a series of windows. LOOK! - no freezers. SEE! how potatoes are sliced. WATCH! as burgers are flipped. GAZE! upon the beauty of a shake being made. Then you pay (using any number of convenient means) and collect your delicious food. Your car then finds an empty space at the adjacent drive-in theater where you enjoy watching clips and trailers that run on a 30 minute loop. When finished, press the "horn" button on your otherwise useless steering wheel, and your car takes you to unload, where it is then wiped down and readied for the next hungry and curious group of guests.
This should of course all take place in some sort of well-hidden warehouse. If done properly, they could ensure a sunset while ordering, dusk until food pickup, then a pleasant twilight for the dining / viewing experience. This would also likely be at least a two lane, perhaps four lane experience, until distribution to the "theater". They would also need some accessible vehicles, as well as "stretch" options for larger families.
If they REALLY want to theme the cars, additional sponsorship opportunities are available.
This stuff practically writes itself...