This is a whole class game that can be used as a brain break that students will love! I have used this in my class for several years. Based on the popular "Twenty Question" game, students take turns bringing a mystery item to school in a lunch sack. Classmates try to guess what's in the sack by asking, thoughtful yes/no questions. Students will get a positive experience getting up in front of their peers as well as understanding and using good questioning techniques in order to guess correctly. It's fun to see how the students evolve from asking random questions to asking good, thought out, questions that very often lead them to the right answer.
This will only take about ten minutes to d, and yet its so much fun for the students. I hope you and your students enjoy this as much as mine have.