What secret message did Ralphie find using his Little Orphan Annie decoder ring?

Ralphie found a secret message that read, "Be sure to drink your Ovaltine." This message, which he decoded using his Little Orphan Annie decoder ring, turned out to be a promotional gimmick for the chocolate drink, leaving him disappointed after his excitement about uncovering a thrilling secret. The moment highlights the disillusionment of childhood and the sometimes mundane reality behind the allure of adventure.