In a medium-sized saucepan over medium-high heat whisk together soy sauce, brown sugar, apple cider vinegar, garlic, sesame oil, and ginger. Heat over medium-high heat and bring it to a simmer.
In a small bowl, whisk together the water and cornstarch then add it into the saucepan. Whisk the sauce constantly until it starts to thicken.
Remove from heat and cool. Use the homemade sauce immediately as needed or store it in a tightly sealed jar for up to two weeks.
