Ad Hoc Fried Chicken Sandwiches with Coleslaw

Name: Ad Hoc Fried Chicken Sandwiches with Coleslaw
Ingredients: 1 Ad Hoc fried chicken brine packet; 6 1/2 cups water; 6 boneless, skinless chicken breast halves, each about 6 oz., pounded to 1/2-inch thickness; 1 Ad Hoc fried chicken coating mix packet; 2 cups buttermilk; Canola oil for frying; 1/2 head green cabbage, cored and shredded; 3 jalapeños, very thinly sliced into rounds; 1/2 red onion, very thinly sliced; 1/3 cup red wine vinegar; 1/3 cup olive oil; 2 Tbs. sugar; 1 1/2 tsp. kosher salt, plus more, to taste; Freshly ground pepper, to taste; 6 torpedo rolls, halved and toasted; Mayonnaise for serving (optional)