Preheat the oven to 350F and spray a bundt pan really well with nonstick spray.
Put the sugar, milk, oil, eggs and vanilla into a blender and pulse until well-blended and smooth. Add the flour, cocoa, baking powder, baking soda and salt. Pour the hot water or coffee overtop (it will start to bubble as it hits the baking powder and soda) and pulse, scraping down the sides of the blender once or twice, until smooth.
Pour into the prepared pan and bake for 1 hour, or until cracked on top and springy to the touch. Let cool for about 10 minutes before turning out onto a wire rack to cool.