Knowing what your volunteers enjoy is a key part of appreciating them. It’s even worth adding a section to their profile in your database in order to keep track of such preferences as snacks, hobbies, etc.
For example, when volunteers come to help with a mailing, I always make sure to have cookies, crackers, and some kind of bread on hand (cranberry nut bread is #1 right now). I used to have muffins on hand, but these were rarely touched. In branching out a bit, I tried some other options and struck gold with ginger snap cookies and the aforementioned bread. Taking a little extra time to figure this out goes a long way in letting volunteers know they are appreciated and make the overall experience far more pleasant when they enjoy the snacks set before them, instead of having to feign enjoyment of dry crackers or who knows what else.
Another practice of appreciation is customizing the food and drinks on hand for your volunteers. If you know one volunteer enjoys herbal tea or earl grey, stop at the store and pick some up. If they are taking the time to help you, then you can at least provide them with a good cup of tea!
The beauty of appreciating volunteers through such tangible means is that it’s always appropriate. I have seen awkward and even tense situations resolved with a box of chocolate dropped off as a peace offering, or a generous amount of attentiveness. It’s hard to be put off when you’re being treated so kindly! So whatever the situation, appreciate, appreciate, appreciate. Going the extra mile to extend some common elements of hospitality will help communicate to volunteers how much they are valued by your organization.