Can red eared sliders eat tomatoes?

Red Eared Sliders can indeed eat lettuce. But a better feeding option would be darker leafed plants such as collared, dandelion and mustard greens. Other vegetable and fruit matter that your turtle can certainly eat and will probably enjoy are shredded or chopped carrot, Apple, squash, green beans(whole or chopped depending on the size of your turtle), and melon.