What vegetables can tortoise eat?

This depends almost ENTIRELY on the species of tortoise.

Some tortoses eat mainly grasses, while others eat mainly broadleaved plants. Some tortoise species eat some vegetables in addition to their greens. Good choices for those species include squash, pumpkin, and carrot (grated). There are exhaustive lists of proper choices for tortoise foods on websites such as Tortoise Trust (see related link to their website)

Correct nutrition is vitally important for the proper growth of a tortoise, and to prevent deformity of the shell.

Avoid spinach, broccoli, cabbage, and iceberg lettuce for all species.