In a saucepan over medium heat, add the sugar, red wine vinegar and an equal amount of water as the vinegar. Bring to a simmer until the sugar dissolves. Then pour the liquid into a bowl and submerge the cabbage in it. Set aside (drain well before using).
Preheat a non-stick pan or grill pan over medium heat. Once the pan is hot, double up the taco shells and heat on each side until they become golden brown. Then set the shells aside in a stack.
Heat the vegetable oil in a large skillet over medium heat. Add the chicken and garlic, browning the chicken while breaking it up into smaller pieces. Add the soy sauce and molasses; simmer for about 3-5 minutes.
For the sauce: In a small bowl, whisk together mayonnaise, Sriracha and lime juice; season with salt and pepper to taste.
Using two shells per taco, spoon the chicken onto the taco shells, top with cabbage, onion, tomatoes, and sauce.