I teach a group of 10 adult professionals. They often come to class bored and tired. What can I do to get them excited about learning English?

Make them start imagining, about a topic which is something common and not too serious, something related to dreams, and accomplishment, something positive inside each person.
I think they all can speak out their minds as well on every topic, and let them share their opinion with one other. Probably bout how they think they can help others proceed with their life on daily basis, what can make themselves happy, in details...and precisely are they feeling healthy ? basic and interesting thing, like entertainment , fun, childhood exciting stories, fun ....

Give them a team work task with verbal instructions only. As they work through the task, remind them to use ENGLSIH ONLY to encourage each other to complete the task.