Drain peaches and pat dry with a paper towel. Sprinkle peaches with cinnamon sugar.

Mix dry cake mix with cinnamon. Cut in butter until mixture resembles coarse crumbs. Set 1/2 of the mixture aside.

Mix peaches with 1/2 of the cake mix mixture; place in a 6-inch round dish. Top peaches with remaining cake mix mixture. Cover dish with foil.

Pour water into a multi-functional pressure cooker (such as Instant Pot). Set trivet inside. Place round dish on top of the trivet. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 12 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, about 20 minutes. Unlock and remove the lid. Quick release remaining pressure using the quick-release method, about 5 minutes.

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler.

Carefully remove dish from the pot and uncover. Broil until topping is set, about 2 minutes.