I've had my slimquick powdered water bottle packets for about 6 months, sitting in my cabinet. Will it harm me or not work as well now? It tastes a lot different from the first time I had it a while ago. Did it expire?

You asked if it expires... yes it does... nearly everything you ingest expires... when will be on the container or in this case packets. It may have been far older than you thought when you purchaced it. It always pays to look at the expiration dates in the store... I've found expired stuff on the shelf next to far fresher stuff. More times than I can count, enough I ALWAYS check before it goes in the basket.