How would you know for sure if that's washer fluid?
I was thinking the same thing, wondering if it wasn't dex-cool that someone drained. Took another look and it appears to be sealed still with the seal pull tab still on the cap.
Actually looking a 3rd time, it might not be a seal ring but just a tab that gets pressed in before unscrewing the cap. Hope it has a foil seal.
It's amazing what people throw away!
We have people who make the rounds regularly so ... nothing of any worth stays in the dumpster long.
I moved to the other side of the city and the people still all have the same schedule.