Where can I store these potions?

Hint 1 of 7:

Where do you normally store your potions?

Hint 2 of 7:

In an empty flask.

Hint 3 of 7:

You won't be able to find an empty flask, but you can make one.

Hint 4 of 7:

You can, for instance, drink their contents.

Hint 5 of 7:

Of course, you should only drink what's meant to be drunk.

Hint 6 of 7:

Like hot water.  There are several bottles on the machine.