Heat a dutch oven over medium heat with 1" of oil (or enough to cover the onion rings). You can use a deep fryer if you have one.In a medium bowl, whisk together 1 cup milk with 1 Tbsp vinegar and let sit 5 minutes. Whisk in ½ cup sour cream.In a separate bowl, whisk together: 1 cup flour, ½ Tbsp salt, ¼ tsp black pepper, and 1 tsp garlic powder.Separate the onion rings and dip each ring in the sour cream mixture, then dredge with flour. (I used a fork to transfer from the wet bowl to the dry bowl so my hands didn't get as gunky). Repeat by dipping in milk mixture a second time and dredging again in flour. Place the finished onion rings on a plate until ready to fry.Once the oil is hot enough for the onion rings to sizzle, place the double battered onion rings in the hot oil and cook for 3-4 minutes or until exterior is crisp and light golden brown. I was able to fit 3-4 rings in my dutch oven at a time. Let onion rings cool on paper towels so soak up any excess oil.Whisk together all of the fry sauce ingredients until smooth, adding hot sauce to taste. Enjoy!