1. Combine shredded vegetables, sugar, and salt in a small bowl. Massage the vegetables with the sugar and salt until well combined. Put in an airtight container and add the water and vinegar. Refrigerate for at least 30 minutes, two hours is even better. Leftovers last at least a week in the fridge.
2. Stir together mayo and sriracha. Set aside.
3. Assemble the sandwiches on the rolls using the spicy mayo, pork or chicken, pickled vegetables, cucumber, and cilantro and jalapeños if using.