How did Sai Baba prove to Cholkar that he knew about his secret sacrifice involving sugar?

Sai Baba demonstrated his omniscience to Cholkar in a subtle yet profound manner. After Cholkar arrived in Shirdi and fulfilled his vow, he went to stay with Jog. As described in Chapter 15, Baba, who did not personally drink tea, specifically instructed Jog to serve his guest, saying, "Give him cups of tea, well-filled with sugar." Upon hearing these meaningful words, Cholkar was completely amazed and moved to tears. This instruction was a direct acknowledgment of Cholkar's secret penance of abstaining from sugar. Baba later confirmed this, stating that Cholkar's vow, the long delay, and the hidden renunciation of sugar were all known to Him, thus confirming Cholkar's faith.