If you like the beach-party-in-the-middle-of-winter idea but don’t have that kind of budget, you can try our version.
Our youth group meets in our home, so we don’t have as much space as a gym, and we only met for our usual 2 hours. We happened to have a sand-coloured carpet, but you could put down beige blankets for sand. We put a tape on with sea sounds and turned up the thermostat. We asked kids to wear (or bring to change into) shorts and t-shirts and bring lawn chairs.
For part of the evening, we put up a net across the livingroom and played beach volleyball with a balloon. They loved it and went back to it after snack time. (We had summer foods like ice cream.) After the sea sounds, we put on the Beach Boys music. It was a lot of fun.