List of e-juices known to crack polycarbonate tanks (originally compiled by ECF's My4Jewels and added to by UKV's members):
Any sour flavours
Any flavours that contain malic acid.
Any e-liquids that contain essential oils
E-liquids that contain triacetin, used in vg liquids to carry flavour more effectively
Cinnamon like "atomic cinnamon" types, not warm cinnamon like cinnamon coffee cake, this is OK
Wintergreen
juice or flavouring
Mimosa
Cola
Nutmeg
Clove oil
Sassafras
TPA Ripe Banana flavouring
...and the list goes on. See? It was at the top of the list!