Sometimes when people assert that a language has no grammar, what they really mean is that there is no grammar book for that particular language. But the rules of a language exist, in the heads of speakers of that language. We know the rules are there because of the way the speakers behave. They use similar structures for similar events. If you hear the sentence for “Give me some water.” in a rarely spoken language such as Spelitzian, you can be pretty sure you can use the same pattern for "Give me some food .", even if, there are other possible patterns as well. If there were not any patterns, people would not be able to communicate because they would have no way of knowing what other people meant to say.