Soak the challah slices in water. Squeeze well and crumble into small pieces, then place the crumbled challah in a large bowl and add the chicken, tapioca flour, garlic powder, salt, and black pepper. Mix or knead thoroughly until well combined.

Preheat the oven to 365 F (185 C).

Prepare a bowl with breadcrumbs. With damp hands, shape the mixture into nuggets and cover in breadcrumbs, removing any excess.

Line a sheet pan with parchment paper and spray generously. Place the nuggets and spray them on top as well. Bake for about 15 minutes. Halfway through, flip them over. If they appear dry, spray a little more oil on top.