Wipe data from dead Android phone
Further to what has already been suggested in the comments, if you're only interested in destroying the data and not recovering it, you could drill through eMMc to completely destroy it.

It is HIGHLY unadvised to do this without careful consideration as your phone contains a lithium ion battery and I shouldn't have to explain the dangers of damaging a battery.

You can follow this guide to remove the "motherboard" from the phone.

I'm not certain where the eMMc is located on the chip (the protective casing covers all the components and I've never done a teardown on the phone myself) but, at this point you can sort of just go crazy and destroy the whole thing.