The sister charms are just attached with jump rings. And the bottle cap has a hole punched in the top of it (I have this kind of hole puncher available -only 1- for $11.50) and is attached with either a jump or split ring. The beaded charms (which I also have available-- 10 for $3.50, 30 for $9.50, 50 for $15 or 100 for $25) are just attached to those rings.
If you're interested in trying out some charms or buying the hole puncher, please email me firstname.lastname@example.org
I've attached some examples of my charms
Hope that helps!