Here is a possibly out-dated list of juices and ingredients known (and suspected) to damage polycarbonate:
http://www.e-cigarette-forum.com/fo...icas-newest-submarine-tank-7.html#post5196472
The Perfumer's Apprentice Root Beer flavouring is one of the ones listed, as well as
any oil-based flavour--so if sassafras oil is used to create the root beer flavouring it will be "dangerous" to polycarbonate. On the other hand, chemically-induced damage to polycarbonate generally manifests as hazing and/or multiple cracks from the onset, so it may well be that there was already a micro-fracture from the cutting of the tubing and the juice is attacking
that--creating a problem that wouldn't have existed without both the pre-existing micro-crack
and the possibly questionable juice.
There is a chance you could mend it with superglue,
BUT--consumer-grade cyanoacrylate glues will breakdown with constant exposure to water/liquid and (it is my understanding that) anything in your juice that may be reacting with the polycarbonate is likely to cause the same issues with cyanoacrylate.
The common DIY fix for making tanks for juices that destroy polycarbonate is to take a syringe or juice bottle with the same inner diameter as the polycarbonate tubing and cut a section of it to fit. Of course doing this will remove the thumbscrew filler hole, but polypropylene is soft enough the drilling a hole smaller than the screw should let it "self-tap" and work.
P.S. if the superglue you are talking about using is specifically labelled for use in aquariums, it should work okay and be fine for use. If the initial problem is with the juice, though, it will likely cause cracks in other areas as well, but using "aquarium grade" cyanoacrylate will at least prolong the life of the tube for quite a while...
