I accidentally
Я по ошибке зашёл в чужую комнату.
I accidentally walked into someone else’s room.
Я по ошибке принял его за своего брата.
I mistook him for my brother.
I drank yours by mistake.
Я по ошибке надел рубашку Тома.
I accidentally put on Tom's shirt.
I took your keys by mistake.
I brought his umbrella by mistake.