Rinse the beans and soak them in water overnight. Be sure to cover them with at least 6 inches of water. They will expand a lot! Drain the beans and rinse well with cold water.
Put the beans in your slow cooker with the broth and garlic. Cover, and set the slow cooker to low for 10 to 12 hours. Add salt and sugar to taste.
Note: If you do not have a slow cooker, you can cook them on low heat on the stove until they are tender.