PREHEAT OVEN TO 325F.
ADD FLOUR, SUGAR, COCOA, BAKING SODA AND SALT TO A LARGE BOWL. STIR TO COMBINE. MAKE 3 WELLS IN MIXTURE.
ADD VANILLA, OIL AND VINEGAR TO EACH OF THE WELLS. POUR IN COLD WATER AND BEAT UNTIL NO LUMPS ARE LEFT.
POUR INTO AN UNGREASED 9×13 BAKING PAN. BAKE FOR 60 MINUTES OR UNTIL A TOOTHPICK COMES OUT CLEAN. LET COOL BEFORE CUTTING.