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

Yes, Chapter 33 of the Shri Sai Satcharita explicitly mentions Udi's effectiveness in curing sleep-related problems through two examples provided by R. Hari Sitaram Dixit. In the first case, his friend had been unable to sleep for eight days and found no relief from a doctor's medicine. After being given some of Maharaj's Udi, he took it that night and reported the very next day that he had slept soundly. In a similar account, a friend's child from Bandra had not been able to sleep for two months. Upon being taken for Maharaj's Darshan in Shirdi, the child got sleep that very night and continued to sleep well thereafter, demonstrating Udi's power to restore natural rest.