Preheat oven to 325. Line a baking sheet with foil and spray foil with non-stick spray.
In a bowl stir together sugar, coffee grounds, cinnamon, and salt.
In another bowl, beat egg white until frothy. Coat walnuts with egg white. Then, pour coated walnuts into the sugar/coffee mixture and stir until well-coated. Spread into a single layer on baking sheet.
Bake 5 minutes. Stir. Bake another 5 minutes. Walnuts should be dry (no longer moist from the egg white) when completely cooked. Sprinkle with sea salt. Cool and store in an airtight container until ready to eat.