The Sixers edged out Sydney rivals the Thunder in the battle of the Big Bash League's two bottom sides on Sunday.
The Thunder chose to bat but none of the side's opening three could get into double figures as Luke Feldman dismissed Chris Rogers and Matt Prior while Josh Lalor clean bowled the dangerous Chris Gayle.
Lalor soon removed Sean Abbott for just a single run as Usman Khawaja did his best to move the Thunder's innings forward down the other end.
The youngster would remain unbeaten on 66 by the end of 20 overs as the Thunder set the Sixers a victory target of 133.
The Sixers began their innings confidently before Nic Maddinson edged Dirk Nannes's victory straight into the palms of Gayle. Fellow opener Michael Lumb went in the next over to leave the Sixers on 29-2.
The dangerous Brad Haddin was also removed by Gayle before a stagnant middle of the Sixers' innings.
Daniel Hughes provided the firepower for victory by hitting a half century as a close finish went the Sixers' way, with the Thunder misfielding and dropping catches in a calamitous end at Stadium Australia.
Defeat by four wickets leaves the Thunder winless after six games in the BBL.
