Chicken Tacos with Pineapple Salsa

Name: Chicken Tacos with Pineapple Salsa
Ingredients: 1 cup tomatoes, seeded and diced; 1 medium red onion, diced, divided; 1 cup diced fresh pineapple; 1 tablespoon chopped fresh cilantro; 1 tablespoon fresh lime juice; 0.5 teaspoon salt; 0.5 teaspoon white sugar; 1 pound boneless, skinless chicken breasts, cut into 1-inch strips; 1 lime, juiced; 8 (7 inch) tortillas, or more as needed; 1 cup shredded lettuce; 8 dashes Sriracha sauce, or more to taste