A former employer used to regularly accuse me of being overly cynical and negative. I’ve never agreed with that assessment. The world we live in does however require a healthy dose of skepticism.
Take for example this claim from the bottom of a carton of Diet Coke:

It’s true. Research shows that all beverages contribute to proper hydration. That means whether it’s your first can of the day or your afternoon pick-me-up, Diet Coke helps you stay hydrated all day long. So stick with the Diet Coke taste you love. Your body will thank you for it.

They even have a web site dedicated to this sales pitch.
I call shenanigans on this claim. Oh, I suppose the statement is true enough. There’s certainly nothing in it you can point to and say, “That’s a lie.” All beverages do contain water, and getting water into your body is what hydration is all about. But there’s some vital information missing.
Most Coca Cola products contain caffeine and caffeine is a diuretic. Putting it as politely as possible, what this means is that caffeine causes your body to lose water by causing you to visit the bathroom more frequently. I don’t know whether the net balance leaves you with more water or less than if you’d skipped the Coke; but if dehydration is a concern, a nice cold glass of water would be a far better choice.
So I don’t agree with the claim that I’m overly cynical. I’m just a little less likely to be taken in by a marketing pitch.