Place tongue in a large stockpot and cover with water. Bring to a boil over medium heat. Boil tongue for 2 hours. Turn heat off and let cool for 1 hour. Peel the skin off tongue and discard.
Transfer tongue to a cutting board and cut into 1/2-inch slices. Coat both sides with teriyaki sauce.
Preheat an outdoor grill for medium heat and lightly oil the grate.
Grill pineapple and tongue slices for 6 minutes; flipping halfway through cook time.