Bring water, rice vinegar, and 1 tablespoon of the sugar to a boil in a small saucepan over medium-high. Combine carrots and radish in a medium bowl; pour vinegar mixture over vegetables, and let stand 15 minutes. Combine mayonnaise and Sriracha in a small bowl; chill until ready to use. Meanwhile, whisk together lime juice, soy sauce, fish sauce, garlic, ginger, 2 tablespoons of the sesame oil, and remaining 1 teaspoon sugar in a small bowl. Place tofu planks in a shallow dish, and pour soy mixture over planks; set aside to marinate at least 15 minutes or up to overnight. Heat remaining tablespoon sesame oil in a large nonstick skillet over medium-high. Cook tofu planks, in batches if necessary, until browned and crispy on both sides, about 5 minutes. Remove from skillet, and immediately sprinkle with salt. Drain and discard liquid from carrots and daikon; set aside. Spread both sides of halved baguettes with mayonnaise mixture. Layer 3 tofu slices per sandwich; top with carrots and daikon mixture, cucumber, cilantro, and jalapeño. Serve immediately.