Preheat an oven to 350 degrees F (175 degrees C). Grease and flour 2 9-inch cake pans or a 9x12 inch baking dish.
Sift the flour and baking soda together in a bowl, and set aside.
Place the eggs, sugar, sour cream, sweetened condensed milk, and vinegar in a large bowl, and beat to combine. Stir in the flour mixture, about 1 cup at a time, mixing between additions to avoid lumps. Pour the batter into the prepared cake pans or baking dishes.
Bake in the preheated oven for 20 to 25 minutes, until a toothpick inserted into the center comes out clean. Cool in the pans for 10 minutes before removing to cool completely on a wire rack. When the cake is completely cool, run a paring knife between the cake and the edge of the pan. Hold the cake pan on its side and gently tap the sides of the pan against the counter to loosen it. Cover the cake pan with a plate or cooling rack, and invert it to tip the cake out of the pan and onto the plate.