Dry granola bars, like those from Nature Valley, can make quite a mess. Reddit user Poke_Red suggests avoiding this problem by microwaving your snack before you eat it.
Ten to thirty seconds in the microwave (depending on your device's wattage) is all it takes to make the bar chewy and less likely to crumble. Obviously, this is less of an issue if your preferred brand is already chewy, but many are not, so save yourself the cleanup.