Take the simpler and easier case of can crushing first.
Electrolytics will discharge in milli seconds but you need microseconds.
Sam Barros (Powerlabs) used 3 kJ of electrolytics and could give some
waist to the can only.
http://www.powerlabs.org/pssecc.htm
Proper pulse caps with 1.5 kJ will tear the can in half easily and shoot
the ends many feet.
http://tesladownunder.com/CanCrushing.htm#CanCrusher2.
You need puck diodes to catch EMF and even then they may blow. I blew
mine at 15 kA.
For coin shrinking, you need much greater energies and I think you
really need pulse caps to do that which don't have the same problems
with reverse voltage.
It took me 5 kJ to shrink a coin.