I just realized that I was distracted when I wrote that and referred to its title; vodka is a good palate cleanser.
As for palate refreshers, I've had good results using sorbets, 'sharp'/tart apple slices, nearly frozen grapes, etc.
Water... Lots and lots of water. Drink it before tasting in order to be super hydrated. This will help you taste more effectively. Swish and spit the water a lot during cupping/espresso tasting. This will wash your mouth and not add a new taste that the next coffee will have to fight like a highly carbonated or sparkling water may. And then drink a lot during the tasting as well.
I know this will sound super crazy to some. But, in order to reset your aroma sensors,... Smell your wrist. Crazy!! I know!! But it works. Try it if you doubt,... Or if you don't doubt, obviously.
Are you enjoying Barista Exchange? Is it helping you promote your business and helping you network in this great industry? Donate today to keep it free to all members. Supporters can join the "Supporters Group" with a donation. Thanks!