How to authenticate food products?
The marks and various labelling quirks might help you but this is something that's going to vary hugely from product to product. Ultimately, I can't see a good solution that doesn't involve talking to the genuine version's creators.


They might be able to explain printing errors or recipe changes,
They should be able to describe their product so you can compare (you could do this yourself),
They might be familiar with existing fakes out there,
They're the people who should be most motivated to end the fraud.


Even if this isn't a counterfeit, you'll help the manufacturer by reporting a dodgy batch. In my experience, they reward this with coupons that usually more than cover a replacement.

If after all this you still suspect something is wrong, you should probably also notify authorities. In the UK we have Trading Standards (local council), Action Fraud (police) and Brand-i (trademark body). You might have similar where you are.

But most importantly, check what you're buying before you buy it. By the sounds of it you've already eaten this stuff and that's just something I'd never do. The food is counterfeit for a reason: it probably doesn't meet standards put in place to protect your safety.