I have various flavors like Hawaiian punch and root beer as the powder you put in your water to make it taste better and it says they were best by last year (2023). Is it safe to use them? I've never even opened the boxes they came in.
Open it up without shaking it up or jostling it too much. Is it still powdery all the way through? If so, it's probably safe.
If you open it up and the mix has any clumps or inconsistent coloring, toss it in the trash because it's likely been exposed to moisture, which invites a ton of potential problems.
Disclaimer: I'm not a doctor, but I have made some questionable decisions with old tubs of G Fuel mix and came out alive, so I'm not just making things up but I'm also not somebody you should trust your health with. Be responsible.