We do shirts, provided by the organization as they are 'required wear' for adoption events. Logo is all the same, but different colors. We got white ones and tie-dyed them last summer and planning to do the same this summer.
I have worked with shelters in the past who did aprons...more costly than t-shirts, and IIRC volunteers had to purchase them. Useful though with the built-in pockets. And badges too, that identified you up close.
#OrganizationalManagement