700x25c tubes inside 700x23c tyre
They'll be fine - I'd certainly use them without question in a 23mm tyre.

Most tubes cover a range like 18-25 and 25-38.  Given 23 and 25 are in the same range I'd expect it to work correctly.

If you have access to a spare 23 and these 25mm tubes, compare them.  I bet they're identical in size, or so close to it that the difference is immaterial.

Tubes are consumables, you'll use them up eventually.

Other options:


Stick one in your saddle bag as the last resort second spare.
Give them away.
Buy a 25mm tyre and try it out (if your bike frame can fit one)