It is misleading to suggest "treat" (as in "my treat", "trick or treat") must be "food" of any kind.
"Treat" is similar to 招待 which could be any services, celebrations, gifts out of courtesy or good will.
2012-03-13 09:35:28 補充：
For example, when you pay the hotel bill, or movie ticket for your friends, you may say "my treat", not just for the restaurant bill. Of course, in case of "trick or treating", most of the treats are the "offering" of candies, not the candies per se.
2012-03-13 09:37:00 補充：
So, in short, the "treat" is mostly the "good will of offering" but the not the foods or the services.
2012-03-13 23:53:07 補充：
Lion Dude must have brought a lot of treats to the meeting yesterday so that we could have the deal done and sealed.
Thanks for the treats - and they are sweets for sure.
2012-03-14 09:33:43 補充：