Ingredients:

1 cup water
1/4 cup soy sauce
5 tablespoons brown sugar
2 tablespoons honey or maple syrup
1 tablespoon mirin (Japanese sweet rice wine) or rice vinegar
2 cloves garlic, minced
1 teaspoon grated fresh ginger
2 tablespoons cornstarch
1/4 cup cold water
Instructions:

Combine Ingredients:

In a small saucepan, combine 1 cup water, soy sauce, brown sugar, honey (or maple syrup), and mirin (or rice vinegar). Stir to mix well. Add the minced garlic and grated ginger.
Simmer:

Place the saucepan over medium heat and bring the mixture to a simmer, stirring occasionally to ensure the sugar dissolves completely.
Thicken the Sauce:

In a small bowl, dissolve the cornstarch in 1/4 cup of cold water to make a slurry. Once the teriyaki sauce mixture is simmering, add the cornstarch slurry, whisking constantly to prevent lumps.
Cook Until Thickened:

Continue to cook the sauce, stirring constantly, for a few minutes until it thickens to your desired consistency. The sauce will thicken further as it cools.
Cool and Store:

Remove the sauce from the heat and let it cool completely. Once cooled, transfer the teriyaki sauce to an airtight container and store it in the refrigerator.
Use:

Use your homemade teriyaki sauce as a marinade for meats, a glaze for grilled dishes, or as a flavorful addition to stir-fries. It can be used immediately or stored in the refrigerator for later use.