Stir the soy sauce, brown sugar, ground ginger, garlic powder, sesame oil, sriracha sauce, and cornstarch together in a small bowl (Note 2). Set this aside.
Slice your tofu block into about sixteen slabs, each between a quarter and half inch in thickness.
Coat the bottom of a medium nonstick skillet with the oil and place it over medium heat. Give the oil a minute to heat up, then add your tofu slabs in an even layer. You can cook the slices in batches if they won't all fit at once. Cook the tofu slices for about four minutes on each side, until golden brown.
Carefully pour the sauce over the tofu. Be sure to split up the sauce if you're cooking the tofu in batches. Let the tofu slices simmer for a minute or two, until the sauce thickens slightly and coats the bottom of the tofu slices. Flip the slices to coat their opposite sides in sauce, then let them cook for a few seconds more before removing the tofu from the skillet and transferring it to a plate.
With the skillet still over medium heat, add the pineapple slices in a single layer. The pineapple can also be cooked in batches if it won't all fit. Cook the pineapple slices for about two minutes, then carefully flip them.
Cook the pineapple slices for a few minutes on the opposite sides, until they're very soft and coated in the leftover teriyaki sauce in the skillet. Remove them from the skillet and transfer them to a plate when they're done.
Slather the inside of each sandwich roll with vegan mayo, then stuff them with the tofu, pineapple slices, and greens. Serve.