If you want to create a simple lapel for an unlined jacket (like a sweatshirt jacket), it just takes a little advance planning.  Before adding patchwork or other embellishment to your sweatshirt fronts, add a 5"-6" wide strip of lapel fabric to the inside.  Cut 2 strips the length of the front and 1" wider than needed to reach the shoulder  from the center front.  Press one long edge under 1/2"; position with the long raw edge at the center and sew folded edge in place.  Trim to shape; baste the raw edges together.  Finish the jacket as you normally would, then fold back the upper fronts to reveal the lapels.