How do you destroy digital media?

It depends on what you want to destroy. If it's a digitally recorded tape, just pull it out of the cassette and stretch it, cut it up or wad it up until it wrinkles.

If it's a CD or a DVD, I usually put mine in the microwave (1000 watts) and set the timer for three to five seconds. It really puts on a light show and smells bad, but you can watch the microwaves eat the metal layer right off the plastic. There definitely won't be anything left of the data.