My friend is having trouble sleeping. Does the Sai Satcharita mention if Udi can help with something like insomnia?

Yes, Chapter 33 of the Sai Satcharita contains two specific anecdotes about Udi helping people who were unable to sleep. R. Hari Sitaram Dixit recounts how a friend of his came to him after being unable to sleep for eight days, despite trying a doctor's medicine. Dixit gave him Baba's Udi to take for three days. The very next day, the friend reported that he had taken the Udi and slept soundly through the entire night. The chapter also mentions a child from Bandra who had not been able to sleep for two whole months. His father took him to Shirdi for Maharaj's Darshan, and on that very night, the child slept well, and his sleep pattern returned to normal from then on.