One of the basic offerings of the Law of Moses was the peace offering. A subcategory of peace offering was the thank offering (Leviticus 7:11-13). This offering, which was made of grain made into some sort of bread, or cake, or pastry, which was unleavened, Unlike the costly sacrifice of an entire animal, a thank offering did not need to be expensive. It was relatively simple expression of what came from the heart.
One of the things about this category of offerings that I have always appreciated is the name that they are given in the Septuagint: θυσίας σωτηρίου, the sacrifice of salvation. There is thus a connection between gratitude and salvation. That is something to be grateful for.