1Bring water,cocoa, and margarine to a boil.
2Add mixture to flour, sugar and salt.
3Mix eggs, sour cream and baking soda separately and then add to mixture and mix well.
4For thinner sheet cake, grease 10 x 15" cookie sheet, or 11 x 13" cake pan for thicker sheet.
5Bake at 350 degrees for 15- 25 minutes, depending on thickness of cake.