I've heard Udi can help with sleep issues. Are there any examples of this in the source material?

Indeed, the footnotes in Chapter 33 provide two distinct examples of Udi curing insomnia. In one case, a friend of R. Hari Sitaram Dixit had been unable to sleep for eight days despite taking a doctor's medicine. Dixit gave him Baba's Udi to take for three days, and the very next morning, the friend reported that he had slept very well throughout the night. In another instance mentioned in the same chapter, a child from Bandra had not been able to sleep for two months. His father took him for Darshan of Maharaj in Shirdi, and that very night, the child got sleep, a blessing that continued every night thereafter.