Heat a grill to medium heat (350° to 450°). In a medium bowl, mix pork, salt, and pepper until just combined (do not overmix). Divide into 4 portions and form into 1/2-in. patties with a slight depression in the center of each to help them cook evenly. Brush burgers with oil.
Whisk together soy sauce, brown sugar, and lime juice in a small bowl to combine. Brush pineapple and Spam slices with soy mixture.
Grill burgers, pineapple, Spam, and onion, turning once, until burger is cooked through, grill marks form on pineapple and Spam, and onion softens, about 3 minutes for Spam and 7 minutes for other ingredients. Grill rolls, cut side down, until grill marks form, about 2 minutes.
Spread bottoms of rolls with mayonnaise. Top with burgers, onion, pineapple, and Spam. Spoon a small amount of coleslaw on each and cover with tops of rolls.
Note: Nutritional analysis is per burger.