Asian chile sauce
A Thai-style chile sauce, Sriracha is made from sun-ripened chiles, garlic, sugar, salt, and vinegar, giving it a hot-sweet-sour-salty flavor profile. Its ketchup-like consistency makes Sriracha an ideal condiment to add a jolt of heat to sandwiches, soups, and other dishes.
Substitute another Asian chile sauce or hot sauce.
Huy Fong is the most widely available brand in the U.S., with its distinctive green squeeze top. It's sold in many well-stocked supermarkets (check the Asian foods section), or in Asian groceries.