No disrespect to handing out team swag and monetary rewards to thank your team--they'll definitely be grateful. But how many times has a superior surprised you with something you truly cared about?
The reason this stands out and is so powerful is that it shows you've taken the time to get to know each team member beyond her contributions at work. Better, you've taken that knowledge and gone out of your way to find a thoughtful gift that relates to her specific interests. For example, if one team member is an American history buff, you could give him a new biography of Teddy Roosevelt. If she's a huge baseball fan, you could snag her tickets to an upcoming game. Is another into music? Get him Spotify Premium. Has she expressed interest in learning to cook, garden, or strengthen her leadership skills? Buy her a DIY book, or sign her up for a workshop or online course.
Finding the right reward for the right person goes a long way toward building rapport. Your team members won't forget the time you got them the perfect gift--which, in turn, will motivate them to keep turning out their best work.