Stir in the tuna, mayonnaise, mustard, relish, pickle brine, juice from the lemon, sugar, and spices until evenly mixed.
1 pound canned or packet tuna, ½ cup mayonnaise, ¼ cup mustard, ¼ cup sweet and sour relish, 2 teaspoons pickle brine, ½ lemon, ¾ teaspoon granulated sugar, ½ teaspoon garlic powder, ½ teaspoon onion powder, sea salt, black pepper