What do you do to motivate Airmen to pass/complete back-to-back EPME courses while they suffer failure after failure?

Match their EPME failure with promotion failure.

So you are asking how do you motivate an Airman to care bout his/her career? Well, I suppose there is no right answer. Counseling them on the fact that this a performance based Air Force that if they don't get their 5 level, they wont promote and they will be out after their enlistment. If they care about that they should be motivated. If not they suffer the consequences. I have seen some sups make their kids come in on off duty hours to study. Don't know if that's the right answer. They should be wanting to progress on their own.

The other question is, why are they failing? Is it because they are apathetic and would rather be in their dorm room playing X-Box? Or do some of them lack academic skills and may need to find a base tutor or be mentored by someone in the unit. In cases there are those people who do not learn the material very well by reading it. Either they have mild learning disability, poor reading comprehension, or they are more visual learners or comb of all three. In those cases they may need someone to help them break down the material so they understand what they are doing. Thats is where you can step in. But if it is a pure motivation issue, short of extra duty or giving them study hours during duty, probably not a whole lot more you can do.