Subway Classic Tuna (Copycat Recipe) You will need: 24 ounces chunk light tuna in water, drained 1/3 cup mayonnaise 2 teaspoons lemon juice 1/4 teaspoon salt 1. Combine all ingredients in a small bowl. Stir vigorously to break chunks of tuna. Chill until cold. 2. Use an ice cream scoop to serve two scoops of tuna on each 6-inch sub roll. Makes enough tuna for three 6-inch sandwiches.