Hindus who strictly follow astrology and caste tradition do not eat certain kind of food on a particular day of a week. This list is based on North Indian astrological tradition.
Monday - Sugar is avoided on Monday. Somwar (Monday) is associated with Chandra – the moon good. Sugar is believed to be the food of Chandra and therefore it is avoided.
Tuesday - Ghee is avoided on Tuesday or Mangalwar. It is believed that it will cause health issues. Mangal, or Mars, is a fiery planet. So eating ghee on Tuesday is like fuel to fire.
Wednesday - One should not eat leafy vegetables on Wednesday (Budhwar).
Thursday - One should avoid milk and milk products on thursday. Banana is also to be avoided on Brihaspativar. The day is dedicated to Vishnu and yellow and milk are his favorites.
Friday - Sour food should be avoided on Friday. In many regions the day of the week is associated with Mother Goddess. Sour food is associated with Goddess in some regions.
Saturday - Oil and food made using oil should be avoided on Saturday. The day is dedicated to Shani and therefore oil is avoided.
Sunday - Salt should be avoided on Sunday. The day is associated with Surya.