When we lived up north we would catch baby turtles and keep them through the summer and release them in time to hibernate.
We fed them worms mostly.
They were eastern painted turtles and what we call leather back turtles. We lived right on the edge of the water and would just catch them by hand. They are cute and pretty while they are small but get kinda ugly when they grow up. The eastern painter looks a lot like a red-eared sliders.
We lived on a channel and it was a kids paradise. All summer long they were catching frogs, fish and turtles....and other things.