Heat the grill to high. In a small bowl, combine the mayonnaise, wasabi and soy sauce, and stir to mix well. Set aside.
Stand the whole pineapple on its base on a cutting board. Using a sharp knife, cut the skin from the pineapple and discard. Cut off the base and the top, leaving a cylinder of pineapple. Place the cylinder upright again and slice downward along the core, to cut away the flesh in large pieces. Place one of these pieces core side down and slice in 1/2-inch thick vertical slices. Reserve the remaining pineapple for another use (or grill for another use).
Place the pineapple slices in a large bowl and drizzle with oil. Use tongs and paper towels to rub vegetable oil on the grate. Place the pineapple slices on the oiled grate and grill for about 2 minutes, just until the slices are marked. Turn and grill for another minute. Put back in the bowl and let cool, then cut the pineapple slices into 1-inch pieces.
Reduce the heat to medium and grill the hot dogs, turning every couple of minutes, until marked and cooked through, about 8 minutes. Spread buns with the mayonnaise mixture and place a hot dog in each one. Top with pineapple and serve with red onion, cilantro and Sriracha sauce if desired.