Preheat the oven to 350 degrees Fahrenheit.
Grease or spray a 9"x13" pan with nonstick baking spray.
In the bowl of an electric mixer, cream together sugar, oil, and eggs. Add canned pumpkin and mix for a short period.
In a separate bowl, whisk together flour, baking soda, cinnamon, nutmeg, salt and cloves.
Add the flour mixture to the wet mixture and mix just until incorporated, scraping down the sides of the bowl with a rubber spatula in between.
Spread the batter into the prepared pan.
In a small bowl, stir together 1/2 c. brown sugar and 1 tsp. cinnamon to make the swirl. Sprinkle it as evenly as possible over the top of the batter and use a butter knife to swirl it into the batter. Swirl up and down and then side to side, in the other direction, as well.
Bake for approximately 25 minutes, or just until a toothpick inserted into the center comes out clean or with moist crumbs.
Place the cake on a cooling rack. While the cake is warm, prepare the glaze by whisking together the powdered sugar and just enough milk for thinning (start with 1/2 Tbsp.). Pour it over the warm cake. If you like more glaze, feel free to double the recipe. Let the cake cool most of the way, then serve.