Does my opponent take a prize card if I knock out my own Pokémon due to confusion?

Yes, if your Pokémon are knocked out in any way, you opponent takes a prize.

Any time a pokemon is "knocked out" the opponent takes a prize card. Look at Forretress ex, for example. It's ability lets you move 5 grass energy from your deck to your pokemon however you like, at the cost of knocking it out. Since it states "knocked out", even though you did it yourself, your opponent takes the two prizes. As opposed to the "hyper blower" iron bundle that states when using its ability you "discard" that pokemon which basically just moves your pokemon to the discard instead of knocking it out, keeping the prizes the same. I hope this helps!

Yes, @JazzyUnicornGir that is incorrect, if your pokemon does damage to itself with a move it has— say Heat Tackle Charmander— and gets knocked out by the damage it takes, your opponent still takes a prize.