If your app runs a sweepstakes, lottery, or contest, you as the developer have to be the actual sponsor with published official rules, eligibility terms, and a legitimate prize-fulfillment process, not just a promotional gimmick with no real backing.
Comes up when a "win a prize" feature is added for engagement without any published rules, sponsor identification, or clear terms.
"Your app conducts a contest or sweepstakes without clearly identifying the sponsor and official rules, per guideline 5.3.1."