Preheat the oven to 350°F. In a large bowl, stir the sugar, flour, baking soda, and cinnamon until evenly mixed. Then add in the egg, vegetable oil, honey, and nuts. Stir until the mixture is smooth. Spoon into an ungreased jelly-roll pan or 9 by 13-inch pan. Bake until a toothpick inserted in the center comes out clean, about 20 minutes. To make the glaze: In a small bowl, stir together the powdered sugar, vanilla, water, and mayonnaise until smooth and creamy. Spread onto the honey bars while they are still warm. Store the bars in a sealed container or cake safe. These will stay fresh for 3 to 4 days.