Eighth seed Machac, who won gold in the mixed doubles at the Paris Olympics, became the third player from his country to win an ATP 500 title, following Tomas Berdych and Radek Stepanek.
"It feels amazing," Machac said after lifting the silver gourd-shaped trophy following his 7-6 (8-6) 6-2 win on Saturday (Sunday AEDT).
Ranked 25th in the world, Machac was the superior player on serve, landing seven aces in a tightly contested first set where neither player could get a break.
Spain's Davidovich Fokina was on the verge of winning the set when he led 6-5 in the tiebreaker, but Machac held his nerve to win the next three points and claim the set.
The 24-year-old stepped up in the second set, getting the first break of the match to go up 3-2.Â
Davidovich Fokina struggled to keep up as Machac won every subsequent game to seal the victory.
Machac, who beat Novak Djokovic in last year's Geneva Open to reach his first ATP Tour final, where he lost to Casper Ruud, fell to his back after securing the championship point in Acapulco as Davidovich Fokina's return got stuck in the net.
"Congratulations for your first title," Davidovich Fokina told Machac at the presentation ceremony. "I don't know how you feel right now, I never won a title, but for sure it feels amazing."
The Spaniard has now lost three finals, including at this month's Delray Beach Open.
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