Not just cinnamon, but a lot of juice cracks polyester tanks. Citrus, colas, banana, pineapple, basically anything acidic. I suggest getting metal tanks, although they claim the V2.5 doesn't crack. I'll believe it when I see it. The metal tanks are cheap enough. GV is supposed to be getting plastic replacements, in colors no less.
GV put the Vivi 2.5s up very late last night. I ordered at 2:00 AM EST and they had only been up a couple hours. I'm betting they'll be sold out before the weekend. If you order one, get the replacement heads. For $1.49, their half the price I've ever seen them before.
I hope you got the Vtube Lavatube and not one of the Lavatubes that are the exact same thing but cost $100. (hint: Volcano).