Fasting is not only from food and drink — guard your tongue, eyes and limbs. The Prophet ﷺ said: “Whoever does not give up false speech and acting upon it, Allah has no need of his giving up food and drink.” (al-Bukhārī). And: “Fasting is a shield; so let him not speak obscenely or act ignorantly; and if someone insults or fights him, let him say: ‘I am fasting.’” (al-Bukhārī & Muslim).
العربية: عن أبي هريرة رضي الله عنه قال: قال رسول الله ﷺ: «مَن لم يدع قول الزور والعمل به فليس لله حاجةٌ في أن يدع طعامه وشرابه». (البخاري).
When fasting (and always), guard your tongue, eyes and ears from sin — that is the true fast.