I believe it is the acidity, but I am not sure. Same results for me until recently when I discovered a new method to purge the large creatures. I ran out of coffee and didn't have time to go to the store. So, I experimented with what I had in the fridge: organic beet juice, carrot juice and organic prune juice. The carrot juice was uneventful, but the beet juice was as successful as coffee and seems to flush out the gunk in my liver or gall bladder that often used to cause pain.
As an aside, after recent radiation treatments for breast cancer, I switched to a clean, plant based diet and had to give up processed Sugar for good. I am now able to fight away the Sugar cravings enough to stop eating fruit and almost all kinds of sugar, which my oncologists claims "feeds the tumors". (Uh, yeah, the *tumors*, I think to myself). But, anyway, it's true that giving up Sugar helps clear the creature problems as well imo. The prune juice is also great to clear the gunk but generally doesn't clear out the large helminths as well as coffee or beet juice. I will warn you in case you decide to try it. Unlike coffee, sometimes the creature may still barely moving and awake, which I find nightmarish. But better to be rid of them and a little freaked out is my attitude. I'll attach a picture as an example if my computer will cooperate.