Spray or generously grease a 9"×13" baking dish with nonstick cooking spray.
Place the bread cubes evenly into the prepared baking dish, and set aside.
Whisk the eggs, coconut milk, coquito, milk, sugar, brown sugar, vanilla extract, nutmeg, and cinnamon in a large mixing bowl until everything is thoroughly combined.
Pour the mixture evenly over the bread, pressing down if needed so that everything is soaked with the egg mixture.
Let it sit for 4 hours or preferably overnight. You could bake it right away if you're short on time, but the egg mixture might not thoroughly soak into the bread.
When ready to bake, preheat the oven to 350℉ (180℃).
Next, combine the topping ingredients, flour, the sugars, cinnamon, nutmeg, salt, and butter, until crumbly, then sprinkle it evenly over the bread mixture.
Bake for 45-50 minutes or until the top becomes golden brown. It should be crispy on the outside and soft inside.
While the casserole is baking, melt the butter for the syrup in a small saucepan over medium heat.
Once melted, add the maple syrup and stir for 3-4 minutes, or until the syrup is heated.
Remove it from the heat and stir in the vanilla, salt, and bourbon. Set aside and serve with casserole.
Remove the casserole from the oven and allow it to cool slightly. Drizzle the entire casserole with the syrup or allow guests to drizzle it over their portions.