Put them up for sale in your Side Shop. Eventually one of the Storm8 bots will come through and buy everything. I was able to sell 10 Green Ugly Sweaters for 1,880 coins, and 10 Red ones for 1,890. Since I had 50+ of each, that helped replenish my coin supply, which took a hit when I had to expand (160,000 coins plus all the expansion papers) to make space for all the event items.