I take a very direct route. Rip the bandaid.

Wait for whatever point to finish on thier end (As you would with normal responses in conversation)

Then, you simply say 'Hey, I'm not going to waste any more of your time. This isn't working.'

Now, it's not as harsh as it sounds if you deliver the message properly. It's not meant to be a heavy handed delivery. It's just sort of a light statement.

Afterwards, usually there's the sort of slow head nod where you let something sink in. Then I'll say something goofy like 'I feel like we should just fist bump and run in opposite directions now'

Now, to be fair, this works with MY personality on dates with WOMEN. I'm pretty good at normalizing jarring things, and I'm also super used to saying jarring things without breaking stride. It changes the tone.

You should experiment with it a bit though and see if you can't get something similar to work for you.

I typically have my dates thank me for being so upfront in these cases, and we both save a lot of time.

Since you're doing it with guys, make sure you do it IN the establishment and see the reaction there in front of lots of people.