In a zip-top bag or a nonreactive bowl, combine soy sauce, garlic, grated ginger, lemon juice, brown sugar, red pepper flakes and canola oil. Marinate chicken in the mixture in the fridge for 3 to 8 hrs.
Heat grill to medium and discard marinade; grill chicken skin side down over direct heat for 5 to 6 min. Turn and cook 6 to 8 min more.
Slice pineapple into 1/2-inch rings and sprinkles each with 1/2 tsp sugar. Grill, turning once, until marked and just soft, about 3 min; serve alongside chicken.
Make this ahead so the chicken has time to marinate. Then dinner is easy to throw together.