When traveling long-distance flights with multiple connections, I always feel 100% better after refreshing myself, changing my socks and shirt.
I’ve found that it’s generally easier if I can locate the family restroom, then refresh in there. I’ll wash my feet, dry them with my Packtowl, then put on a fresh pair of socks. I also will wash/rinse my armpits and apply fresh deodorant, and change my shirt. The aforementioned Packtowl is wonderful when traveling.
I’d recommend packing a change of clothes in your personal bag, which I do.
But since I also don’t check bags, I have everything that I need with me at any rate, whether packed in my personal bag (smaller) or my carry-on (bigger, mostly clothes and laptop).
After a quick 10-minute refresh in the family bathroom, I always feel so much better, cleaner, and ready for the next leg of the journey. This is especially true after 6+ hour, long-haul flights.