The Torah returns to the revelation on Sinai in Chapter 24 and adds an extra dimension, that of individuals, having a personal revelation of God. But there are significant differences between the two versions.
Previously we were told that the people had to wait at the bottom of the mountain while Aaron and the priests went half way up and then only Moshe climbed to the summit to commune with God and receive the Torah. This week we are told the Seventy Elders went up with the priests as well. And they “saw” God. “And they saw the God of Israel and under His feet it was like pure sapphire as pure as the as the sky.” I understand this to mean that they experienced a degree of enlightenment far more intense than the rest of the people down below. It reminds me of the story in the Talmud of four great rabbis who entered paradise (Pardess) and Rabbi Akivah warned the when they came to pure stones not to imagine they were water. Appearances are deceptive but they certainly experienced something abnormal.
But the why does it say they then ate and drank? Some people think that experiencing God or a mystical reality raises them up automatically to a higher level than ordinary mortals. But it does not in the sense that they still must eat and drink and do all the physical things that everyone else has to. They are not super humans.
The fact that they ate and drank immediately afterwards teaches us that the spiritual world is there to help us live better and more meaningful lives, not necessarily to put us above other people. And this is reflected in the way we go about our lives daily, even in such mundane acts as the way we eat and drink.