Preheat the oven to 350 degrees Fahrenheit. Spray a 9x9 baking pan with cooking spray.
In a small bowl, combine arrowroot starch and water. Whisk to combine then set aside. In a separate small bowl place raisins and whiskey and set aside.
In a large bowl, combine almond milk, applesauce, coconut milk, vanilla extract, maple syrup, salt, cinnamon, and nutmeg. Whisk to combine. Add arrowroot starch mixture and whisk again to incorporate. Add the cubed bread to the mixture and then gently fold with a large spoon or rubber spatula until most of the bread is saturated.
Transfer the bread mixture and any remaining liquid to the prepared baking pan. Strain the raisins from the whiskey (save the whiskey) and sprinkle them over the top. If making vanilla sauce, the whiskey will be used there.
Brush the tops of the bread cubes with melted butter. Bake for 45 minutes to an hour, tenting with foil at the 30-minute mark (50-55 minutes was perfect for me). The result should be golden and slightly crisp on top and a bread pudding custard consistency on the bottom.
To Make Vanilla Sauce: In a small saucepan, add almond milk and arrowroot starch. Whisk until arrowroot is dissolved. Add the remaining ingredients and turn to medium-high heat, whisking often, for about 3 minutes. Lower heat for one minute and then remove from heat.
Serve bread pudding with a generous drizzle of vanilla sauce on top of each serving.