1Stir sugar and apple cider vinegar together in a small saucepan; cook over medium-low heat until sugar is dissolved, scraping sides of the pan to include all sugar granules, 3 to 5 minutes; remove from heat and let cool 2 to 3 minutes.
2Combine vinegar mixture, olive oil, soy sauce, sesame oil, garlic, and red pepper flakes in a food processor; blend until the garlic and red pepper flakes are tiny, 1 to 2 minutes. Strain through a fine-mesh sieve.