Coca-Cola has distributed bottles of its drink with yellow caps around the same time each year for the past several decades. You might wonder what the cause of the cap change may be, and the answer goes pretty deep.

Yellow caps are indicators for those who celebrate Passover. During Passover, people of the Jewish faith practice eating "kosher" foods, and cannot eat or drink anything that is not labeled as kosher, including foods or fermented drinks coming from wheat, barley, oat, spelt, or rye.

Most Coca-Cola sold in the United States is sweetened and made from high-fructose corn syrup, which does not meet the kosher standard. However, the yellow caps on Coca-Cola bottles indicate to those celebrating Passover that that bottle was flavored with non-corn-based sweeteners and is therefore kosher.