Mark 9:29 Prayer and Fasting
It may take longer than one day to fast and get the results your asking. The purpose is to weaken the flesh. An idea might be like 2 days fasting then break with some light food (rice or bread) and water then 2 more days fasting break light food and water then so on… I recommed reading about fasting and ask your pastor.
In my situation I did this several weeks and fasting helped me a lot. If I get back into battles I know just to fast and the enemy just leaves me alone because I feel Gods presence so clearly… and the enemy is no where to be around!