Heat oil in medium saucepan over medium-high heat until hot and shimmering but not smoking, about 2 minutes; add onion and cook, stirring occasionally, until softened and beginning to brown, about 5 minutes. Add garlic, chili powder, coriander, cumin, salt, and sugar; cook, stirring constantly, until fragrant, about 30 seconds. Add chicken and cook, stirring constantly, until coated with spices, about 30 seconds. Add tomato sauce and ¾ cup water; stir to separate chicken pieces. Bring to simmer, then reduce heat to medium-low; simmer uncovered, stirring occasionally, until chicken is cooked through and flavors have melded, about 8 minutes. Pour mixture through medium-mesh strainer into medium bowl, pressing on chicken and onions to extract as much sauce as possible; set sauce aside. Transfer chicken mixture to large plate; freeze for 10 minutes to cool, then combine with 2 cups of cheese and jalapenos in medium bowl and set aside.
Adjust oven racks to upper and lower-middle positions and heat oven to 300° F.
Smear entire bottom of 13 by 9-inch baking dish with ¾ cup chili sauce.
Place tortillas on two baking sheets. Spray both sides lightly with cooking spray. Bake until tortillas are soft and pliable, about 4 minutes.
Place warm tortillas on counter-top. Increase oven temperature to 400° F. Place ⅓ cup filling down center of each tortilla. Roll each tortilla tightly by hand and place in baking dish, side by side, seam-side down. Pour remaining chili sauce over top of enchiladas. Use back of spoon to spread sauce so it coats top of each tortilla. Sprinkle remaining ¾ cup of cheddar cheese down the center of the enchiladas.
Cover baking dish with foil. Bake enchiladas on lower-middle rack until heated through and cheese is melted, 20 to 25 minutes. Uncover and serve immediately, garnishing with sour cream, avocado, lettuce, lime wedges, etc. Yield: 4 to 5 servings.