As best I can tell so far, it seems to be just some kind of coded trend to indicate your relationship status. As with the last major trend like this, it was rumored that it was to spread awareness of breast cancer, but I’m not seeing any signs that point to awareness of a different topic just yet.
Like the previous trend, in my experience so far, the status seems to largely be propagated by women. The system goes by the following general pattern:
Blueberry: I am single.
Pineapple: It’s complicated.
Raspberry: I am a touch and go woman.
Apple: I’m engaged.
Cherry: I’m in a relationship.
Banana: I am married.
Avocado: I am the “other one”.
Strawberry: Can’t find the right one.
Lemon: I wish I was single.
Grape: I wants to get married.
I got the code from this page, and figured it was a women-only thing because part of the code (for Raspberry) refers to being a woman.
If anyone has any further details, please post in the comments and provide your reference.