How exactly did Sai Baba manage to light the lamps when the grocers refused him oil?

According to the detailed account in Chapter 5, after the grocers refused him oil, Sai Baba performed an extraordinary act. He returned to the mosque and found his tin pot, which had a tiny bit of oil remaining. He poured water into that oil and drank it himself, making it an offering to the Supreme. He then took plain water, poured it into all the lamps, soaking the dry wicks. When he lit them with a match, the water burned as if it were oil, and the lamps stayed lit all night long.