Breakable Bottles
First, you have to make a mold to put your candy glass into. You should use a silicone mold, and maybe strengthen it with a plaster mother mold.
A really good book on mold making is "The Prop Makerīs Molding And Casting Handbook" by Thuston James. If youīre interested in fx and breakaway casting buy it. You can check out other good books here: Required Reading
Still, itīs difficult to make a bottle from sugar glass, Iīve found it much easier to make from thermoplastic resin. This is still hard, and the resin is a little espensive. You have to use a glass-blowing kind of system to do this, too.
I hope this at least gives you some ideas!
If you want bottles to get blown up in a gunfight, try something like this:
Use a bottle that has a small hole drilled in the bottom. Then tattach some wire to the cork/cap on the top, run it down through the hole in the bottom and through another hole drilled in whatever the bottle is standing on.
Then attach something heavy to the wire and gives it a feet or two of slack and attach the heavy thing to a mechanism that holds it in place - but when released allows the heavy thing to drop the one or two feet - making the bottle violently collapse!
This should look just as somebody blew the bottle up with a gun.
If there's no actors around you could use real bottles (but the whole crew should still wear eye protection) but bottles of sugar glass is safer. Mind you I just saw a program where a stuntman said you COULD still get cut on sugar glass if you tried.
