In a post here at CZ, Moritz instructs to take half a teaspoon in a large glass of water -dilute well-, and to drink two of those glasses everyday for six days. -I use a 12 oz. glass or even more- (slowly throughout the day, presumably in the same way as given for the apple juice (between meals, avoiding drinking it during, right before, and in the first two hours after meals, and in the evening).
Especially avoid drinking it after you'eaten, I did it once, then lied down -burned my throat. Beware.
Yet it is quite acidic. I do both, actually, juice and malic, as I can't stand either for too long continuously, and most likely will do the Coke flush 3-day prep instead next time; six days = too much for me.
As for other options, it mentions cranberry juice -contains much malic acid-.