Noun for something you dabble in

In three words, this could be called a passing fancy:

a passing fancy

Something that captures one's interest or enthusiasm for only a brief period of time.

_{Jim was really into learning about horticulture for a while, but it turned out to be only a passing fancy.}

_{I played a few sports during college, but they were all just passing fancies.}

_{She sure spent a lot of money on that fancy camera, so I really hope photography isn't just a passing fancy for her.}

_{Source: The Free Dictionary}

Historically, an avocation was exactly this, but it has gained a more formal tone and today implies a more serious level of devotion and usually concerns a respectable subject matter.

Today, I'd just call it a pastime.

How about a dalliance:

brief or casual involvement with something

"Berkeley was my last dalliance with the education system."

Source: Oxford Languages

Dalliance is most commonly used in a romantic sense, but it can also be used in other contexts to suggest similarities to a passing fling.

I think fad may suits your request:

an intense and widely shared enthusiasm for something, especially one that is short-lived.

(OLD)