To be honest, the best thing my facility could do to show how much they appreciate us is by staffing adequately all the time, instead of leaving us with skeleton crews all the time and routinely trying to call in extra help. Should be the other way around: PLAN for the high load, and give people the option of time off when census drops. Show your nurses you value them by not making them so stressed to come to work that they drink Pepto-Bismol instead of coffee on the way in!
But that probably doesn't help you much for a one-week program
Ok. They say there's no such thing as a free lunch, but make that untrue: give away certificates to the cafeteria for free meals, to be used whenever the employees want (like when they're working doubles and didn't plan to) or coupons to trade for vending machine money for when the cafeteria is closed (like for us night people, who oftentimes have to rely on the Fridge for Hire).
Along those lines, make it a perk that when the census IS high, and you know staff isn't getting time off to get food (truly, sometimes not even to eat it), you SEND FOOD IN. That's right: if you know your night staff is getting screwed over because of high census and short staffing, make SURE there is a sandwich tray all made up, delivered to unit. They at least know they can grab a bite when they pass the breakroom, if not take time out to prepare something themselves.
We don't need a coffee mug or plaque or fuzzy greeting card. Do something that makes our shift genuinely better to get through.
I would love it if my hospital did that: show they know how hard we work and the time we spend on it by picking up the tab and providing the meal. But you know what? I'd sooner expect to see adequate staffing than THAT happen!