An occupational hazard (and occasional benefit) of expertise consulting is forming a wide range of opinions broadly and at depth within your areas of expertise. Within any given conversation, meeting, proposal, architecture, codebase, and so on, you’re likely to have something to contribute: war stories, outside perspectives, things you’ve seen work well, tensions you can spot.
One really great option (which I’m as guilty as anyone of not exercising enough) is simply keeping your mouth shut.
Give it a minute. Your client is the expert on what they themselves want; given the space, sometimes they’ll arrive at the same conclusion you might’ve suggested. And the greatest value you can offer isn’t always the outsider’s spit-take; just as often, it’s the ability to soak up context and then re-share it later in a different shape than you’d found it.
(By all means, though, whatever you were thinking you wanted to share, write it down for yourself! Not only does it feel about as good as saying it aloud, but it may well have been a good idea, and this way you’ll remember it for later.)