How do you say "trick or treat"?
Is it a word for word translation or is there a more common use of terms?
Hi yoga, there is really no translation for that in Spanish as the celebration does not include to go from house to house to ask for sweets.
However, you could say something like:
¡dame dulces o te convierto en rana!
I only managed to find a dictionary explanation. But you may find this link interesting.
Truco o dulce