In a small saucepan, add 1/2 cup of soy sauce, 1/4 cup of water, and 1/4 cup of honey. Whisk together until well combined.
Stir in 1 tablespoon of rice vinegar, 2 teaspoons of chili flakes, 1 teaspoon of minced garlic, 1 teaspoon of grated ginger, and 1 teaspoon of sesame oil. Mix thoroughly to ensure all flavors meld together.
In a separate small bowl, mix 1 tablespoon of cornstarch with 2 tablespoons of cold water until smooth. This will help to thicken your sauce.
Place the saucepan over medium heat and bring the mixture to a gentle simmer, stirring occasionally. Once it starts to bubble, add the cornstarch mixture while continuously whisking. This will help to thicken the sauce.
Allow the sauce to simmer for another 2-3 minutes until it reaches your desired thickness. If you prefer a thicker sauce, let it simmer a bit longer.
Remove from heat and let the Spicy Teriyaki Sauce cool before transferring it to a storage container. It can be stored in the refrigerator for up to two weeks.