Sandwich vending machine are used for fresh food, you can use a carousel where the customer can shop his item or an equipment with spiral where you will use a First in first out (FIFO) system. Both equipment are good for a vending machine, but what is the most important thing is the quality and the variety of the fresh food you put into the fresh food vendor. There is so much offer from the outdoor (restaurant, c-store, etc) you have to compete with them and bringing attractive fresh food into a vending machine will make the people buying from it and they will be happy.
Frozen vending machine is also an interesting equipment because you can put item for longer than a fresh food vending machine. You can put attractive meal that people can eat right now with a microwave or bring it at the house after the day at work. You can also sell cold dessert during hot time like popsicle, frozen yogourt, fudge, etc.