One wonders here if the pronoun it might have been accidentally dropped after the verb brake. When we consider all the Book of Mormon passages that describe the distribution of the sacrament (including this one), we find three passages in the original text where there is no direct object after the transitive verb give, in addition to the one case here in 3 Nephi 18:3 where the direct object for the verb break is also lacking (in the following list, I represent each of these missing direct objects as NULL):
There is evidence elsewhere in the Book of Mormon text that the it after the verb give is optional; for discussion, see under Alma 55:31.
When we consider similar passages in the King James Bible, we find the same kind of variation, especially when we note that in the English translation the it is in italics, which means that the it is missing in the Greek original (in the following, each of these cases is represented as it/0):
(The last three New Testament examples, it should be noted, do not involve the Lord’s supper. And in the last one, Paul is the agent, not Jesus.) In the Greek original, the direct object pronoun it never appears in these verbal conjuncts. In the King James Bible, we get a mixture: sometimes the it is supplied, sometimes not. Most important of all, there is one case in the King James text where the it is lacking after the verb break (in Luke 24:30). The pattern of variation in both the King James Bible and the Book of Mormon argues that the pronoun it is intentionally missing here in 3 Nephi 18:3. The same holds for the it that is frequently missing after the verb give in these Book of Mormon passages. The critical text will therefore follow the earliest reading with respect to these potential instances of the direct object pronoun it. Interestingly, there is one case involving the verb give (in 3 Nephi 20:4) where the it was supplied in the 1840 edition (see under 3 Nephi 20:3–5 for discussion).
It is also worth noting here that in the Gospel accounts Jesus blesses the bread (or gives thanks) before breaking it, but in the Book of Mormon he does the opposite: he breaks the bread first, then blesses it (just as the priests do in the LDS church today).
Summary: Maintain the lack of it after the verbs break and give in 3 Nephi 18:3, 3 Nephi 20:3, and 3 Nephi 20:4–5; in these cases, the direct object pronoun it appears to be intentionally missing.