what the hell are you doing?An informal, rude way to question what someone is doing. กัน indicates that more than one person is involved, or that the speaker is addressing a group; the exact pronoun depends on context. วะ, ว่ะ, and นะ can make the expression sound even more casual or emphatic.
TH: พวกเธอทำบ้าอะไรกันอยู่ รีบออกมาได้แล้ว!
EN: What the hell are you doing? Come out already!