Now what was "three measures of meal" here? There's a law—a principle of Bible study—that says (it's called the law of first mention), "the first time a thing is mentioned in the Bible influences how it should be interpreted throughout." What we have here is the first time "three measures of meal" is used. It's used in the context of a fellowship meal—giving hospitality, and to God—so it has a spiritual connotation.
We need to learn a little bit about Israelite dry measures. The smallest unit of measure is an omer. Three omers equal one about one seah. This seah is what is translated "measure" in Matthew 13:33, except it is in Greek saton. There is also the ephah, which is ten omers. Three seahs made up of about three omers equal one ephah. These verses show that the smallest meal offering that could be given was one seah, one-third of an ephah. It had to be of fine flour. Abraham gave three seahs, three measures. He went above and beyond what was required for the meal offering.
I think he recognized immediately who it was.
This meal might have been the very first fast food meal in the history of the world, but fast food by our standards it was not. It is also unusual that Abraham did not even eat with them.
One of the things of course that we can learn from this and add to our fund of knowledge of the way food and eating is used in the Bible is that it is the focal point of Abraham and Sarah—the father and the mother of our faith—as their means of hospitality. It is not unimportant.