Cut 12 cider donuts into eighths and allow them to sit out on the counter for a day so that they are stale.
Once the donuts are stale, make the bread pudding. In a large bowl, whisk 4 eggs.
Add ¾ cup granulated sugar, ¼ cup brown sugar, 1 cup half and half, ¼ cup whole milk, 1 ½ tsp cinnamon, 1 ½ tsp vanilla, ½ tsp baking soda and ½ tsp salt to the bowl. Mix until fully combined.
Add 4 tbsp melted butter into the combination and mix again.
Place all stale donut pieces in an ungreased 9×13 pan.
Pour the liquid mixture into the pan with the donut pieces, and use a rubber spatula to stir the donut pieces around so that each cube is coated in the mixture. Allow the donut pieces to soak for about 15 minutes.
Place in the oven at 350 for 40 minutes.
Remove from the oven and cover the pan with aluminum foil. Cut slits in the top of the aluminum foil and then place the pan back into the oven for an additional 10 minutes. The bread pudding should be set but not dried out. It should also not be too liquidy.
Allow to rest for 10 minutes.