I've been having trouble sleeping. Does the Sai Satcharita mention if Baba's Udi can help with insomnia?

Yes, Chapter 33 provides two specific anecdotes about Udi helping with sleep problems, as recorded by R. Hari Sitaram Dixit. In the first account, Dixit's friend had been unable to sleep for eight days, even with a doctor's medicine. Dixit gave him some of Maharaj's Udi, and the very next day the friend reported that he had slept very well throughout the night. The chapter also mentions a child from Bandra who had not been able to sleep for two months. After his father took him to Shirdi for Baba's Darshan, the child got sleep that very night and continued to sleep well from then on.