Well, today, I have just "gifted" a Golden ticket to the brilliant senior cabin crew on my LCY flight. He went out of his way to make my very short remarkably pleasant and was just great with every other passenger in the CE cabin despite a full flight. I did that after I arrived, and if I remember correctly, he will never know it was from me which is exactly the way it should be.

If you want to thank flight attendants, I suggest you use Golden tickets/ well done. That actually is the done thing (or at any rate what BA has devised as our primary avenue to express gratitude to those who go above and beyond to give us great trips) and I personally find it a lot less awkward than a $5 coffee voucher which could almost come across as slightly patronising even though I@m sure it would be meant in the best possible way.