Spray a quarter sheet pan lightly with cooking spray. Line the sheet with parchment paper, then spray the top of the paper with a light even coating of cooking spray.
Finish prepping the sheet pan by giving it a light sprinkle of flour all over.
Add the sugar, milk, oil, vanilla, and eggs to a large mixing bowl. Use a hand or stand mixer to mix the wet ingredients until well combined, about one minute.
Add the flour, baking powder and salt to the bowl. Mix the dry and wet ingredients together on low speed until they form a smooth creamy batter.
Pour the chocolate chips into the bowl. Use a rubber spatula or wooden spoon to gently fold the chocolate chips into the batter by hand.
Use a large spoon to dollop all of the cake batter evenly over the prepared quarter sheet pan. With an offset spatula, or the back of a spoon, smooth the top of the cake batter inside the sheet pan.
Place the cake in the preheated oven and bake it for 24 to 27 minutes, or until the edges of the cake are golden and beginning to pull away from the sides of the pan. The top of the cake may look pale after baking, but should feel firm to the touch of a fingertip.
Remove the sheet cake from the oven and cool it on a wire rack before decorating it with frosting (optional). You can leave the cake in the sheet pan to serve if you like, or you can remove it and serve it on a platter or overturned baking sheet.
Once cool, top the cake with your favourite icing or frosting. Finish with a sprinkle of chocolate chips if you like.