Nic Maddinson's 59 not out led the Sixers to a target of 129 and an eight-wicket win over the Thunder in the Big Bash League Sydney derby.
Maddinson hit nine fours in his 56-ball innings and put on an unbroken 87 with skipper Moises Henriques (27no) for the third wicket as the Sixers - who had already qualified for the semi-finals - got home with four balls to spare.
The Thunder made a total of 128-6 after being sent in at Stadium Australia, opener Daniel Hughes top scoring with 32.
Australia Test spinner Nathan Lyon was the Sixers' star turn with the ball, picking up 3-14 including Hughes from his four overs.
The result is the Thunder's seventh defeat in eight matches and means they finish the season bottom of the eight-team league.