Is teriyaki sauce just sweetened soy sauce?

Not exactly. Teriyaki sauce typically contains soy sauce as its main ingredient. It also contains sugar, mirin, and spices. This mix creates a rich, sweet-savory flavour.

Which is healthier: soy sauce or teriyaki sauce?

Soy sauce is lower in sugar but higher in sodium. Teriyaki sauce has less sodium but more calories due to the addition of sugars. Moderation is key with both.