I had a buddy that used lime juice to dissolve it since it wouldn't break down in water. I guess this is what you're talking about and you already know what time it is. Sorry. Anyway, I saw him and others doing that, over a long time, and I never heard of a single issue. Some people even used vinegar, but I assumed that would be too strong and just couldn't be wise. Maybe they diluted it first.
Those little juice bottles sit at room temperature. The juice has most likely been pasteurized, and being loaded with natural preservatives (citric acid, vitamin c), and at such a low pH, they sure wouldn't be friendly to microbial growth. But that is not to say it is *definitely* sterile.
I heard a gal mention using vitamin C tablets, or I guess just a little piece of one, but it would likely have some pill-filler/binder that would not dissolve. Now biggy if it were just a tiny bit, of course, but nothing worse than pulling through a lil cotton ball with a ton of crap that didn't disolve.
Here's a thought. Citric acid, in powder form, is used in canning tomatoes and things. It is in the baking section of grocery stores, like around the spices and baking supplies. That would be worth checking into, I think.