I had a couple helium tanks leftover from the kids' birthday parties, so I figured I'd take a whack at reusing them. Here's how to attach 1/4" OD tubing to one. From there, you can use it to store compressed gases (e.g. CO2, air).
Disposable helium tank (the ones I have are Balloon Time)
1/4" OD compression nut with insert
1/4" OD tubing
3/16" drill bit
5/16" drill bit
Disclaimer: Author is not responsible for loss of life, limb or property. Author is not responsible for anything. In fact, author is completely irresponsible. I mean, you should see some of the stuff he gets up to. It's amazing he hasn't burned the house down yet. Don't listen to him. Seriously.
Step 1: Cutting
Remove the nozzle. Cut the connector off as close to the thread as possible. There should be a small plastic nib inside. Remove that.