Mix the soy sauce with the sugar and oil until the sugar is dissolved.
Rinse the turkey steaks under cold running water and pat dry. Place the pineapple slices in a flat bowl and sprinkle with pepper. Spread the marinade evenly on it with a brush and cover everything with cling film in the refrigerator overnight. Possibly turn after a few hours.
Place the meat and pineapple on the hot grill and grill for 10-15 minutes, turning several times.