Preheat the oven to 325 degrees F. Beat the egg whites and 2 tablespoons water in a large bowl with a mixer until slightly stiff peaks form. Add the snack mix and toss until evenly coated.
Generously coat a 3-quart ovenproof bowl with cooking spray and place the snack mix in it. Crumple a large sheet of foil and mold into a bowl shape about one-third the size of the 3-quart bowl. Coat the outside of the foil bowl with cooking spray and press into the snack mix to make a well in the middle, forming the snack mix into a bowl shape.
Place the bowl with the foil in the oven and bake until the snack mix sets, 30 minutes. Remove from the oven and let cool slightly, 5 minutes. Carefully remove the foil. Cool 30 more minutes, invert the edible bowl onto a plate and cool completely.