Ukraine trailed inside five minutes as Lee Kang-in converted from the penalty spot, but Supriaha found the net either side of half-time and Heorhii Tsitaishvili rounded off the scoring late on.
Saturday's final in Lodz featured two first-time finalists and it was Korea who made the brighter start thanks to Lee's spot-kick, awarded after VAR ruled Kim Se-yun had been fouled just inside the area.
Supriaha profited from some slack defending to tap in an equaliser in the 34th minute, however, and he added Ukraine's second early in the second half after being inadvertently played in by Korea's Kim Hyun-woo.
Ukraine had Real Madrid goalkeeper Andriy Lunin to thank for keeping them in front when he pushed Lee Jae-ik's header on to the frame of the goal.
And Tsitaishvili scored a breakaway third to round off the comeback for Oleksandr Petrakov's side, who saw off Panama, Colombia and Italy on their way to the final.
