Salaam , I was on my fast today but nobody knew it . I just kept it secretly for some specific reason . An hour before the maghrib prayer my mother phoned me and and told me to come to my aunt's house cause she has gone to pay her a visit . I drive to my aunt's house . When I entered the house , my aunt showed some formality and she made me to eat a cake and drink some juice I unintentionally drank it . But I swear I didn't put anything in my mouth before maghrib's adhaan , Is my roza(fast) vaild ?
Yes, your fast is valid.
The Prophet (ﷺ) said, "If somebody eats something forgetfully while he is fasting, then he should complete his fast, for Allah has made him eat and drink."
I don't think you need any more proof.
The Prophet(pbuh) said: “Whoever forgets he is fasting and eats or drinks, let him complete his fast for it is Allaah Who has fed him and given him to drink.”
So you don't need to make up for that day of fasting.
But make sure you'll be more conscious when fasting next ramadan in sha Allah.