system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 When a beverage is advertised as "More hydrating than water," how could that be physically possible? Or is that just marketing nonsense?
gpt
This is marketing nonsense that stems from a tiny grain of truth. 

**The grain of truth**

To be properly hydrated, you don't just need water, you also need salt and other electrolytes. As an example, when you sweat, it is salty, so if you sweat a lot, just drinking water won't fully replace what was lost, you also need ~~sweat~~ **salt**. Realistically, the vast majority of people do not lose enough electrolytes to need to use these "extra hydrating" electrolyte beverages. But if you are exercising super, duper hard, or if you have really bad food poisoning, they can help. 

**The marketing nonsense**

Not sure how it works elsewhere, but in the US, companies are allowed to say anything about their product as long as they are not claiming it treats a specific disease. If you look closely you will notice lots of vague but healthy sounding statements such as "more hydrating than water" or "supports (body part/system) health." These are meaningless phrases.