Peel and quarter your peaches. Place them in the dutch oven. Sprinkle your sugar on top of the peaches. In a separate bowl mix the white cake mix and your can of 7-Up. The mixture will be lumpy. Pour the cake mixture on top pf the peaches. Put lid on your dutch oven.
Place dutch oven on top of about 20 coals and place about 10 on top. Depending upon the heat of your coals it will take about 15-20 minutes but check occasionally to see if the cake is a golden brown.