If before the first date, it seems to scupper the chances of a connection and ruins some mystery.

If during the date, they might not be interested in a casual thing and you've just wasted your time.

If after sex, it seems a bit douchey.

It seems like there is no optimal timing. And how do you frame it? Do you say "casual", "something not serious", "fwb"?

Thanks for any advice given.