Grease a bundt pan with nonstick cooking spray and set aside.

Add cake mix and soda to a mixing bowl and mix well. Mixture will be fizzy from the carbonation in the soda. Just mix gently until the cake is mixed well. Pour into prepared pan.

Cover the cake with a piece of paper towel and cover the paper towel with foil. Loosely wrap the foil around the pan.

Create a sling by using a long piece of foil and folding it in half. Place the pan onto the center of the sling and bring the ends up toward the sides to the center.

Place 1 cup of water into the bottom of the instant pot. Place the trivet into the pot and place the cake into the pot. Tuck the foil down into the pan if it is extending beyond the top of the pan.

Place the lid onto the instant pot and secure the lid shut. Close the pressure release valve. Set the instant pot to manual, high pressure for 45 minutes. When the cooking cycle is complete, open the pressure valve with a hot mitt. Open the lid and carefully remove the cake by lifting the sling out of the pan. Be very careful as the water in the pan is hot and so is the cake!

Place the pan onto a protected surface and remove the foil and paper towel. Let set until cooled completely.

Invert the pan onto a serving platter or cake plate and sprinkle with powdered sugar and vanilla ice cream before serving.