I am assuming the vehicle is not insured for this. If it is, my recommendation would be to contact your insurance company and not mess with the vehicle.
I hope it was fresh water that flooded the vehicle. If it was salt water you chances of saving it are slim. Even if the vehicle was flooded with fresh water, you likely have a mess on your hands.
Slow down. I wouldn’t try to make anything on the vehicle work until it is thoroughly dried out. In the mean time, do what you can to prevent any additional damage. Disconnect the battery and cover that open window with plastic to keep out any rain.
I agree with what “Melanie” wrote, except I would pull all of the plugs. If you see water in the cylinders, pump or suction it out. Another option would be to disconnect the starter’s electrical connections from the vehicle and energize it with a jump pack to spin the engine over, which will push the water out of the plug holes. Put a small amount of fresh motor oil, Marvel Mystery Oil, or type F transmission fluid into each cylinder, and crank the engine over by hand for a couple of revolutions to coat the cylinder walls with the oil. Replace the sparkplug to keep anything from getting into the cylinders.
Consider draining and filling the engine oil, transmission fluid, and differential grease, to be on the safe side. Your power steering and brake hydraulic systems should be sealed against water intrusion, but it wouldn’t hurt to check them, just to be sure.
Powering on electronics while they are wet is likely to damage them. Unfortunately, it sounds as though you might already have done that, but obviously you cannot change that, so just do what you can to prevent further damage.
Ideally, you want to get all standing water out of computer modules, other electrical and electronic components, and electrical connectors as soon as possible, because they will quicky corrode when wet, but that might take hours of work. If you do want to try, you can use a combination of WD-40, contact cleaner spray, and compressed air to dry electronics and connectors.
You may need to replace your seatbelt pretensioners if they got soaked. I’m not sure about whether that would be necessary if your airbag light doesn’t come on.
Make sure you look in your trunk for signs of water intrusion and damage.
I have heard about a similar situation where the seats and all the carpet had to be removed from the vehicle because of mold formation, but I think that was an almost new luxury car, and IIRC, it got totaled in the end by the insurance company.
That’s all I can think of off the top of my head.
You may want to have the vehicle towed to a shop to have some or all of the work done by professionals. They may spot things you would miss, but obviously going that route would be much more expensive.
You may have to make a tough decision about how far you are willing to go to try to fix your car.
