Nagula Chavithi is the day people in Andhra Pradesh worship Nagas or snakes. This festival falls on the fifth day after Naraka Chaturdashi (This year Nagula Chavithi is on
October 27, 2014 November 15, 2015 November 3, 2016, October 23, 2017). On this day, in my home, we fast through the day; worship nagas; offer naivedyam of Vada Pappu, Chalimidi, Chimmili, Panakam, bananas, and milk; and eat at night after the Mangala Aarathi. The only food we eat is that offered as naivedyam.
Traditionally, women visit the nearest pamula putta or snake pit to pray to the snake god. If a pammula putta is not accessible (as is the case in Mumbai), we make an idol of the snake god with wheat flour and offer prayers to this idol. On the next day, this idol of the snake god is either immersed in a water body or left on a tree as a symbolic way of returning him to nature.
Read more about Nagula Chavithi at http://theancientindia.blogspot.in/2012/11/nagula-chavithi-festival-for-snake-god.html
Here are the recipes for Nagula Chavithi Naivedyam.