Edit: nvm, I should have just explained rather than asking and not waste your time, my apologies.
Reason I asked is that while nothing in those flavor packets spoils in a way that will harm you, nor break down into something that could, they may well taste unpleasant.
Artificial sweeteners in particular kinda get “stale”, unless stored completely air free. They lose sweetness, and if the other chemicals are mixed with the sweetness in mind, it might not be enjoyable.
But there’s no actual expiration date on any of the brands or their components that I’ve ever seen. Best by dates aren’t the same thing as expiration dates (which you probably already knew, but figured I’d mention it anyway).
Worst case, it tastes like crap, unless the package has been damaged enough for moisture to get in. If the packet is intact, you’re good to go. Otherwise trash it