In non-reactive saucepan (such as stainless steel), combine vinegar, 1 cup (250 mL) water, sugar, garlic, pickling spice, salt and red pepper flakes. Bring to a simmer over medium heat for 5 min.
Meanwhile, place coleslaw mix in large heat-proof bowl. Pour hot pickling liquid over top. Let stand 30 min. Cover and store in refrigerator up to 3 days.
Serve Quick Pickled Slaw with burgers, grilled meats or pulled pork.