Hello!

We offer free t-shirts to volunteers who are in certain positions, but not to everyone. At a previous organization, we offered t-shirts to everyone as part of their uniform. (They were expected to wear them at their shifts to identify them as staff who has access to non-public areas of the building.) We offered them one shirt when they started as part of their registration fee of $25, which covered their shirt and their background check, and then they could purchase additional shirts at a discount. 

Generally, it's a good idea to stay away from gift cards for volunteers. It can create sticky legal situations because it is like offering cash for services, but at way below minimum wage. Many organizations have a strict policies against gift cards for that reason.

Also, the IRS places limits on the monitory amount of gifts that can be given to volunteers and staff without tax consequences. It may be a good idea to check in with your finance department about that.

It's good to be aware of the potential for imbalance in public recognition. Maybe you can talk with staff about spreading the love around more intentionally.

Good luck!