In a large mixing bowl, combine water, soy sauce, brown sugar, honey, ginger, and garlic. Whisk together.
In a small bowl, combine cornstarch and water. Mix well.
Pour the first mixture into a medium saucepan and cook on medium heat (about 5 minutes).
When the sauce begins to boil, add the cornstarch mixture and whisk continuously.
When the teriyaki marinade begins to thicken (about 2 minutes), remove from heat. Allow to cool to room temperature.
In a dish or freezer bag, coat the chicken in 3/4 of the teriyaki marinade and place in the fridge for at least 1 hour.
Place the chicken thighs on the grill, discard marinade, and baste with reserved teriyaki sauce.
Cook for 5 minutes, flip, and baste with more sauce.
Grill chicken thighs for an additional 5 minutes or until the internal temperature reaches 170 degrees F when measured with a meat thermometer.
Top with a sprinkle of sesame seeds and serve.