How did Sai Baba prove to Cholkar that He knew about Cholkar's secret sacrifice?

Sai Baba demonstrated His omniscience to Cholkar through a simple yet profound act involving tea. As Chapter 15 recounts, after making his vow, Cholkar had to delay his trip to Shirdi due to financial difficulties. During this time, he secretly gave up eating sugar as a personal penance. When he finally visited Shirdi and was about to leave with his host, Jog, Baba specifically instructed Jog to give Cholkar "cups of tea, well-filled with sugar." This instruction was astonishing because Baba himself did not drink tea, and more importantly, Cholkar's renunciation of sugar was a secret. This act left Cholkar amazed and tearful, as it was undeniable proof that Baba knew his innermost thoughts and sacrifices.