Usually I just chase it with something sour. We buy those little bottles of concentrated 'water enhancers', so I just make a strong glass to chase the kava.
I have had some luck mixing in some cocoa and half&half. Just throw 1-2 teaspoons of cocoa in the bag with your kava before kneading. A little goes a long way. I have been tempted to throw a shot of espresso in the mix to make an iced kava mocha.