Here's my bottle making recipe:
Go to Lowes Hardware, and look for drawers of plumbing stuff - find the A-86 PB226 (WATTS brand) 1/8" x 1/4" I.D. HOSE BARB to FIP ADAPTER (or the very similar A-85). I'm sure other brands/types will do, but that's the one I'm familiar with and use. Anyway, it is brass, I believe. Buy a handful, as they are pretty cheap and great to have around.
Here is the hose barb thingie:
Then, get your juice bottle cap, and drill a hole smaller than the barb of the hose barb adapter, then shove the hose barb adapter through the bottle cap from the underside, so the barbed end goes through. Make sure to press hard so it is flush. The big base of the adapter will prevent leaks and the pressure of the Co2 will keep it pushed up and flush (but you may want to remove the bottle cap to attach airline so as not to push it down). Bingo! you are ALL done! finito! No silicone, no 24 hours to dry, nothing! Ready to use!
I suggest the big, heavy juice bottles, or the Dannon 1 gallon water bottles if you can find them. They are not like normal one gallon water bottles, but clear and much stronger. They have a little handle (see last photo) on the cap/neck as well for easy carrying. (forgive me please that the bottle cap is dirty, I grabbed one just for illustration, it isn't one I had been using).
I also use T barbs to connect two bottles together. This produces A LOT of Co2. I have found, however, that it is best to change them both at the same time when you renew.