Herbs like cilantro and parsley are perfect for small birds. Parsley is high in vitamin A and C, which makes it both healthy and delicious. The left over long stems make a fun, shreddable toy for small birds.
Garlic can be deadly to birds just the same as cats and dogs. Some people do feed it, but it's fed in a mixture and the birds may get a very tiny amount. I would hate to recommend garlic and say it's okay, then have something feed too much and kill their bird... so best to avoid.