How did Sai Baba demonstrate his omniscience to Cholkar regarding his secret vow about sugar?

The demonstration of Sai Baba's omniscience is a key moment in Chapter 15. After Cholkar finally arrived in Shirdi and fulfilled his vow, he was a guest of a man named Jog. As they were together, Baba suddenly instructed Jog, "Give him cups of tea, well-filled with sugar." This statement was profoundly meaningful because Cholkar had secretly given up sugar as a penance for delaying his vow, a fact unknown to anyone else. Baba himself did not drink tea, so his specific instruction about adding plenty of sugar was not a casual remark but a direct sign to Cholkar that his secret vow and long penance were fully known to Baba, which brought tears of joy to Cholkar's eyes.