I don't keep hingeback tortoises, and am not familiar with their diet, but I THINK it depends upon which sub species of hingeback you have. Do you know which?
This is what my friend Google has to say about your question:
Kinixys are insectivorous and omnivorous in nature. In the wild, they will eat fruits, grasses, snails, slugs and millipedes. If they are in captivity, they get a little less choosy in their habits and will eat melon, tomatoes, peaches, slugs, earthworms and oranges.