Step 1

In a blender or with an immersion blender, mix together sugar, tomato paste, dijon mustard, rice vinegar, garlic, ginger, soy sauce, pineapple, salt, pepper, and sriracha.  Set aside 3/4 cup of the marinade.

Step 2

Put the chicken thighs in a medium bowl and mix with the remaining marinade. Marinate for at least 4 hours and up to 48 hours.

Step 3

Heat the grill to high and brush grill grates with oil if needed. Drain the marinade off the chicken thighs and place them on the hot grill. Close the lid and cook for 2 minutes. Flip the chicken, baste it with the reserved marinade and cook with the lid closed for another minute. Continue cooking, flipping, and basting this way for about 10 minutes until the internal temperature registers 185F degrees.