Pour water, brown sugar, soy sauce, honey, garlic, and ground ginger into a small pot.
Bring the mixture to a boil and let it cook over medium heat for about 5 minutes.
Dissolve cornstarch in a little cold water in a small bowl until you have a smooth mixture without lumps.
Pour the cornstarch mixture into the sauce and let it simmer until it reaches the desired consistency. It should have about the same consistency as liquid honey (the sauce will thicken a bit when it cools, so don't make it too thick). If it does, you can simply dilute it with a little water.
Cool the sauce and pour it into a cleaned bottle, jam jar, or similar.
The sauce can last a couple of weeks in the fridge.