One of my favorite giveaways to do on various platforms, is something I call a Code Streak. It's a randomly paced code giveaway in which I continue to post new codes so long as the person who redeemed it posts what kind of pack they received.
All it takes is one wrong answer for me to close the Code Streak. It's completely based on human nature. If the person who redeems a code wants me to keep posting codes, they need to tell me what they got. But if the person who redeems a code either doesn't want me to continue posting codes, ruining the game for everyone else, or doesn't want to be seen participating, then it's over.