Swap Meet Achievement in Rocket League
Trade and receive one or more items with another player in a single transaction
How to unlock Swap Meet
By playing online you have a chance to unlock uncommon items, rare items, very rare items and crates. Some events grant you limited items as well. When in a party with another player, select their player icon at the menu and invite to trade. Each player must add one or more items in the box. Hit start to complete the transaction.