何すんの

what are you doing?

→ 何
phrase Rare #34,567
what are you doing? An informal contraction of 何するの, often used when questioning someone's actions. Depending on tone, it can sound surprised, annoyed, or accusatory; it can also mean “what will you do?” in some contexts.
JA: そんなところで何すんの?
EN: What are you doing there?

何すんの

What are you doing?

— 万引き家族 (2018)

陽菜勝手に何すんのハンバーガーお礼のつもり

(Hina) You... what the hell are you doing? Is this your way of thanking me for the hamburger?

— 天気の子 (2019)

何すんの

What are you doing?!

— フィフス・エレメント (1997)

あんた何すんの

What the hell are you doing?!

— セントラル・ステーション (1998)

具体的に何すんの

What exactly are we going to do?