Brisbane elected to bowl first after winning toss and it looked like an inspired decision after 11 overs by which time the Thunder were only 1-71, having managed just five boundaries.
But after doing a great job of pinning Sydney down, the Heat bowlers lost their way badly, as the Thunder plundered 111 runs off the final nine overs to reach their biggest total of the season.
Late fireworks from Daniel Sams (36 off 15 balls), Alex Ross (25 off 12) and Oliver Davies (16 off 10) helped propel the Thunder to an imposing total of 6-182.
Sams was especially destructive, hammering four sixes, including back-to-back efforts off Mitchell Swepson, one of which sailed into the second tier.
Earlier in the innings, Rilee Rossouw (39 off 35) and Matthew Gilkes (37 off 35) combined for a 57-run second-wicket partnership to lay down a solid foundation for the Thunder.
James Bazley, who was the only inclusion to the Heat line-up for this match, was the pick of the bowlers, taking 4-22 from his four overs and finding himself on a hat-trick in the final over.
Mark Steketee (0-48 from four) and Swepson (0-35 from three) copped the brunt of the Sydney punishment.
The Heat will need 9.15 an over to win and lift themselves off the bottom of the ladder.
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