Spray the slow cooker with nonstick cooking spray.

In a large bowl, stir together the granulated sugar, brown sugar, and cinnamon. Set aside.

In a separate small bowl, whisk the egg whites and vanilla until slightly frothy.

Add all the nuts to the slow cooker. Pour the egg white mixture over them and stir until the nuts are fully coated.

Sprinkle the cinnamon sugar mixture over the nuts and stir again until everything is well coated. Cover and cook on low for 3 hours, stirring every 20 minutes.

When 20 minutes of cook time remain, pour 1/4 cup warm water into the slow cooker and stir.

When the cooking time is complete, spread the nuts onto a parchment-lined or silicone-lined baking sheet and let them cool until dry.