Is opened Teriyaki sauce safe to use after the expiration date?

Yes, provided it has been stored properly, the bottle is undamaged, and there are no signs of spoilage (see below) - commercially bottled Teriyaki sauce will typically carry a Best By," "Best if Used By," Best Before, or "Best When Used By" date but this is not a safety date, it is the manufacturer's estimate of how long the Teriyaki sauce will remain at peak quality.