I brain-gamed my two a bit on the afternoon walk, most of it training related. In fact, I think all of it is training-related, because I'm either teaching them steadiness (how to wait and watch rather than dive in), or generally working on their handler focus.
Mostly brain-game:
I had them sit and wait and chucked a few treats into some old tractor tyres on the edge of a field and then let them find them (scent work plus going into a confined space)
I got them to sit next to each other and then called them to me one at a time (I've only just started this, so it was a bit hit and miss!) (Focus on handler, self-control)
Then training more than brain-game:
Practiced off-lead heel with both on my left (a shambles, they distract each other)
Continued teaching the older dog to walk off-lead to heel on my right, which is a radical departure from what she's always been taught, which is to walk to my left, while the younger one was on-lead on the other side
Then brain-game more than training again:
Got them to jump up onto logs in the woods and perch there, mostly so I could take cute pix (agility, balance, confidence)
They enjoy all of this - they like the interaction, treats and praise - and it helps with things like their focus on me when walking off-lead (so less free-hunting - they are both prey-driven) and their lead manners. And the bonus was that they were pretty chilled all evening.