faddish
It's the hot thing now, but it'll be old news by next week.
My friend bought that new phone. Now he's showing it off to everyone. I bet he'll get a new one in a month.
My sister got a new perfume. She's wearing it everywhere. I think she'll get tired of it in two weeks.
My brother started a new diet. He's eating only fruits now. I bet he'll give it up in a week.