Sinkfield, who had three RBI, has hit five homers in the last four games.
The Hawks took a 2-0 lead in the first inning, but the Eagles scored a run in the second, two in the third, and one in the fourth to go up 4-2.
After Hillsborough tied it with a pair of runs in the bottom of the fourth, Polk State went ahead with a run in the sixth and added three insurance runs in the eighth.
Miles Simington went 4-for-4 with a double, a triple, three runs, and an RBI.
Rhys Cratty had a pair of singles and three RBI.
Nico Limoncelli went 2-for-4 and scored a run.
Zach Scott doubled and scored a run.
Chase Ashby had a single, a sacrifice, and a run.
Starting pitcher Pat Doudican (2-6) earned the win. In seven innings, he gave up four runs (two earned) on five hits, walking two and striking out five.
The Eagles (24-20, 11-11) play Hillsborough again Friday at 5 p.m. at Bing Tyus Yard in Winter Haven.