Can you use soy milk past the expiration date

Does it say "Sell by" Or "Best By" instead of an expiration (Use by) date?

There is a diffrence.

If you have kept it refrigerated properly, and not let it sit out unduly long in super warm weather, not on the radiator or stove, there's no reason you can't use it beyond the date on the carton -- which BTW is NOT a "use by" date, but a "sell by" date.

The same is true for milk (the stuff that comes from cows). Of course, the marketers want you to think otherwise, so they can sell more milk. But if you have doubts, taste it. Your tongue will know.

Unless it is chunky it should be okay. I would still give it a taste before using it.