from weak sauce, this refers to anyone who messed something
up, failed at an endevour, or otherwise failed to meet certain expectations/standards through inexcusable inaction.
Willy: Wassup playboooiiieeee?! I heard all ya'alls got laid last night!
Bruce: Fuck ya playa, everyone besides Clarence. He was dipped in weak sauce.
Willy: He always is...