Feeding pots should be very strong. I use glazed earthenware as they are heavy and easy to keep clean. I use water bottles with stainless steel spouts fixed from the outside of the bars.
Chipmunk food can be bought pre packed but is expensive. I personally use fruity parrot food as a basis and add to this oats, wheat and corn.
They love all types of nuts. Peanuts are a favorite I buy these in their shells and try to hide them under logs etc. They also like hazelnuts, again I leave these in their shells and hide them. I collect acorns and pine cones from the park.
Fresh fruit and vegetables should also be given. They will eat most fruit in season I put in apples pears and oranges whole along with other fruit. They like some vegetables, cauliflower being one favorite along with fresh peas when available. Avoid lettuce.
There are many other foods they will eat including dog food, dog and cat biscuits and fresh scraps of chicken. I sometimes buy live mealworms for them.
Make sure you give them a varied diet.