CopyKat.com is the creation of Stephanie Manley. Stephanie started publishing recipes on the web in 1995 as a means to capture her family recipes in a format that they would not be thrown away.
Over the years 
Sonic Onion rings are made fresh every single day. I worked at Sonic as a teenager and had to help make the sonic onion rings EVERY DAY…the secret is using vanilla ice milk mix, but using melted vanilla ice milk works just as well.
Sonic Onion Rings Recipe
Sliced and separated Spanish onions
Pan or bowl of water
Pan or bowl of all purpose flour
Pan or bowl of melted vanilla ice milk
Pan or bowl of ground corn meal
Cookie sheet for air drying
Place above items on counter in order listed. Dip onion in water, then flour (shake off excess), dip in melted ice milk, then corn meal. Gently shake off excess and place on cookie sheet to air dry for at least 20 minutes.
Fry until browned.
Sifting the flour and corn meal once in a while keeps lumps out and makes it easier to coat the rings When placing on cookie sheets to save room, lean on top of each other to allow entire ring to dry.
I also made thousands of Sonic onion rings. We used 50/50 milk/ice cream mix, then in the flour, then in 100% ice cream mix, then cracker meal. Works great with squash or green tomatoes, etc.
Yes, it was cracker meal. I remember that too. Fried pickles are made in the same fashion.
What is “vanilla ice milk”?
Using milk with a bit of sugar works well also. I use sugar water.