Juice is not reccomended, because as the PPeH and everyone says it only adds to the volume of the liquid you have to drink, without really making the taste better. You can't hide it completely. So it would only make things worse.
What you may want is something with high sweetening power adding the least volume possible. So the best thing are artificial sweeteners or plain sugar. Maybe syrup like grenadine or mint if you want to add a "flavor".
Most important thing in my opinion, is to commit to swallow the whole thing as fast as possible. It will help the most in overcoming the bad taste and will guarantee you will be able to take the whole quantity. After that, best thing you can do says PPeH would be ingesting some alcohol, both to overcome N taste and to potentiate its effect.
So do not obsess over taste. As bad as it can be, it will be just a matter of minutes.