Combine mustard, apple juice and 4 tablespoons of cider vinegar in a large bowl, as the marinade.
Slightly score the sausages, creating more surface area for the marinade. Marinade the sausages until coated or leave them overnight.
Set up the BBQ so it has hot heat on one side, medium heat in the middle then indirect heat on the other side.
Once they have marinated, place the hot dogs over the hot heat first and bunch them together so they hold each other in the same place. Wait until they have coloured (5 minutes), then place them over the indirect heat, close the lid and turn the outdoor grill into an outdoor oven and cook them all the way through (10-15 minutes).
Add vegetable oil to pan then thinly slice the onion. Add flour, a teaspoon of garlic granules, cayenne pepper, cracked pepper and some salt to a bowl and mix in the onions to coat.
Place the onions into the pan to fry.
For the Alabama white sauce, add mayonnaise, horseradish, Worcestershire sauce and remaining garlic and vinegar into a bowl and stir.