Many are assuming vapors tongue is due to the transition off smoking. I can tell you in my experience its not - I never smoked (other than the occasional cigar) and I've been hit with it.
Taste is part of the nervous system, and like any other continuous stimulation, the nervous system acclimatizes and desensitizes it and shuts it out, reducing the "gain" of the signal so to speak. In taste terms that means a reduction in taste intensity. Things that were once flavorful become dull and tasteless. Smell does the same thing.
Changing juices is one strategy, temporarily reducing vaping is probably the quickest way to get taste intensity back, but of course is problematic and in the case of a smoker using vaping to get off smoking, can very well drive them back to smoking.
There is a principle in muscle building workouts called muscle confusion. When doing strength training its very effective to vary the routine. The body in general is prone to migrate to a homeostatic state. Taste is part of the same neurological framework, so I think the same strategy applies - taste confusion (ie: changing stimulation) or removal of the continuous stimulation is to my thinking the best strategy for dealing with this.
I don't know how much this helps you understand the problem but you might be able to come up with solutions that deal with this 'taste exhaustion' effect. Like I said, red wine works for me, along with changing juices. YMMV.