There are companies who handle data destruction for a fee - many of the shredder companies have added this line of business.
The DIY method I recommend is to use one of the available multi-pass data destruction a.k.a. disk-wipe tools to write random 1s and 0s onto disks over multiple passes until the disk is truly wiped.
We have had companies hire us to do this, or alternately remove disks prior to equipment being sold to salvagers.
You can then donate them as you see fit, or you could install Ubu and use them as patient education tools that you have taken into a room.
