Snackis is a false friend for English speakers. It doesn't mean 'snack' (that would be mellanmål or literally 'in-between-meal') but refers to a popular topic of discussion.
In order for something to be a snackis, it should be topical — something that's in the news or relevant right now — and something that most people have a basic level of knowledge of and have their own opinions on.
Basically, a snackis is something everyone's talking about, and in fact the word comes from the verb snacka ('to chat').
You could translate it in English as 'talking point', 'hot topic', or 'talk of the town'.
Something might be a snackis in general — a topic that's being discussed in the news or on social media currently — or it might be the snackis of a specific event, such as a football match, an awards ceremony, a party or a neighbourhood community meeting.
A snackis can be something serious, such as a scandal or crisis, but it can also be something completely trivial such as a piece of gossip or someone's haircut or outfit.
The key thing to ask yourself is, has it got people talking? If so, it's a snackis.
Händelsen har blivit en snackis
The incident has become a hot topic
Hennes klänning var Nobelfestens stora snackis
Her dress was the big talking point of the Nobel Prize ceremony