There's no faster way to get a DUI Class Certificate of Completion than taking the class online. That's going to be much faster than a scheduled in-person class where you have to go the same time every week. Online classes are self-paced which means that you can complete the class as quickly as you want.
Most people take 1-2 hours of classes per day. But if you are willing to work hard you can do 4 hours per day or even more. So that means a 12 hour DUI class could be completed in 3 days or less. A 24 hour DUI class could easily be finished in a week.