I'm thinking of visiting Shirdi and was considering fasting. What was Sai Baba's opinion on fasting for spiritual gain?

Sai Baba held a very clear stance against fasting as a spiritual practice. The narrative in Chapter 32 explains that Baba himself never remained fasting and would not permit anyone else to do so either. He reasoned that a fasting person's mind is not peaceful, making any spiritual benefit impossible to achieve. He taught that God is not attained on an empty stomach and that the 'trouble of fasting and penance' does not work with him. This philosophy was demonstrated when a woman named Gokhale came with the intent to fast, a plan Baba already knew and intended to prevent.