At the beginning of Operation Little Saturn, in the Russian campaign (it's one of the tank levels), turn immediately to your left and find a single tree sitting on the slope of the embankment that doubles as the level's collision wall. Drive up the embankment directly to the right of the tree and right through the level's collision wall. From here turn to your left and locate a road that follows around the mountain away from the rest of the level. Continue down the road and in about 30 seconds to a minute to should see a large red apple in the distance. Continue driving into the apple to find one of the strangest thing I've ever found in a WWII game... Besides a 20 story giant red apple, at least.