How come Koro sensei had tomato juice inside jail?


In Assassination Classroom Season 2, episode 8, Tadaomi was fighting with
Reaper, and then there was one incident where he faked his death from blood
loss with the help of Koro-sensei. And then later it is shown that Koro-sensei
was drinking tomato juice, and with the help of his one tentacles he faked
that scene and helped Tadaomi.

So my question is: how did he get that tomato juice? Is it possible that he
was keeping it from the start, or did he try to escape and then got one?

[![enter image description
here](https://i.stack.imgur.com/49I7o.jpg)](https://i.stack.imgur.com/49I7o.jpg)




Explained in the manga:

[![Chapter
109](https://i.stack.imgur.com/lweZ4.jpg)](https://i.stack.imgur.com/lweZ4.jpg)

He bought it beforehand.




Explained in the manga:

[![Chapter
109](https://i.stack.imgur.com/lweZ4.jpg)](https://i.stack.imgur.com/lweZ4.jpg)

He bought it beforehand.

