How to physically erase iPhone memory?

My iPhone 4 broke. I think the battery messed up or something but it completely died. It won't charge at all, can't turn it on, and when I plug it into my laptop nothing happens. I have a new phone so I don't really wanna bother with my 4 anymore, but if I toss it I wanna make sure the memory is erased. Is there a way to wipe it when it won't turn on. I don't have a tiny screwdriver or anything. Will putting it in water wipe the data in it?

Added (1). Is there a way to somehow erase the memory without completely destroying it? I'd like to maybe sell it for parts or give it to someone or something.

If it won't connect to the computer it is impossible to wipe it. But if you want you could probobly just smash your phone so that it is un usable, then destroy the memory card.