Making your own Teriyaki Sauce is easy. It's cost effective and taste a lot better than what you get from the commercial bottle you buy from the store, minus all the preservatives, artificial flavorings, and other unhealthy additives to keep its shelf life longer.
Here's a recipe which you can use as a sauce or a marinade. You can also put it in a bottle, keep in the refrigerator, and it would last for about two weeks or more. Just double the ratio if you want to make more.
1/2 cup soy sauce (use Japanese soy sauce)
1 cup Mirin
3 tablespoons sake wine
1/3 cup sugar
5 slices ginger
3 cloves minced garlic
Put everything in a sauce pan and bring to a boil. Turn down heat to low and simmer for about 20 minutes. Let cool.
* Makes about 1 1/2 cups Teriyaki Sauce