Clean off the mud, install a new battery, and add some fuel is all it takes to bring these crushed cars back to life.
It's easy to forget how much of an engineering marvel that the internal combustion engine is. A network of precisely engineered pieces can carry you hundreds of thousands of miles with relatively minor maintenance. For a true torture test, see what happens when some Russians try to start a Lada and Toyota after burying them in a marsh for a year. Warning: there's some slightly salty language in these videos, so keep your surroundings in mind if watching without earbuds.
From the beginning, the host is confident about getting the Lada going but is less certain about reviving the Toyota. Sure enough, getting the Russian vehicle going isn't too hard. The job requires getting the mud out of the air intake, cleaning off the spark plugs, and installing a fresh battery. Make sure the exhaust can breathe and spray some starter fluid into the carb. After a little wheezing, the powerplant comes to life. While not shown in this video, the host also changed a gasket on the carburetor.
As expected, the Toyota engine isn't quite as easy to restart. Much of the work is the same, including getting all the much out of the intake, adding a fresh battery, and cleaning the spark plugs. There's lots of water in the engine, too, but turning it over with the spark plugs out of the way pumps the liquid out. Once done, the Russians add a little fresh oil. The mill briefly comes to life by spraying starter fluid into the carb but not for long. Some gasoline is enough to get things going, though.
To see what these machines looked like before they went into the mud and when they came out, check out the video below. The vehicles were certainly worse for wear after a year underground. The weight of the earth crushed them, and it was a particularly wet year so dirt flooded into the broken windows. The guys weren't very careful when pulling the cars out of the hole, either, including ripping the front end off the Lada.