Heat water, orange juice concentrate, salt, brown sugar, rosemary, peppercorns, bay leaves, and garlic in a pot over medium to a boil. Cover pot and remove from heat; let cool 20 minutes. Stir in ice until melted; let cool 10 minutes more.
Place turkey breast on a cutting board skin side down. Using kitchen shears, cut through ribs, following vertical line of fat where breast meets back, from tapered end of breast to wing joint. Using your hands, bend back away from breast to pop shoulder joints out of sockets. Using paring knife, cut through joints between bones to separate back from breast.
Submerge breast in brine, cover pot, and refrigerate until ready to roast, at least 2 hours, or up to overnight.