... it's the end of a Sprint, and it's been a very good sprint.
Management and the product owner must appreciate and exhibit genuine concern for process improvement.
Process improvement is a central Scrum activity. It takes time, yet the time is worth it. It is a time to reflect not only on the opportunities for improvement but the successes of the sprint as well.
It is actually good to be a bit Pavlovian and to reward behaviors as close to the behavior as possible. You could have a group party as in Celebrate Success, but that takes more time. And it's also important to hold the sprint review as close to the end of the sprint as possible. Having a celebration first would break the continuity.
Therefore:
After a particularly successful sprint, or a sprint that is otherwise worthy of celebration, rent a sauna for the sprint review. Start the meeting with a very information review of the sprint activities, focusing on both good and bad as usual. As the meeting goes on, segue into the social side of the event and allow it to continue into the night. Be sure to include local food and some champagne.
Keep the celebrations infrequent enough so that they are special.