Or HaChaim on Exodus 34:28/אור החיים על שמות ל״ד:כ״ח

1 לחם לא אכלתי, "I did not eat bread, etc." The reason that the Torah specified that Moses ate neither bread nor drank water was to make us aware that he did absorb nutrients of a different kind. He absorbed spiritual food. We find something of that nature in Psalms 40,9 where David speaks about תורתך בתוך מעי, "Your Torah being in my entrails." Torah is also compared to water in Taanit 7. Had the Torah merely written: "he neither ate not drank," this would have included all kinds of "food."