ZD, the Prohibition Amendment clearly spelled out religious exemptions, so it was not necessary to go to the First Amendment.
Minor nitpick: The amendment itself said nothing about religious practices. It was the Volstead Act (which governed how the 18th was enforced) that made the exemption for religious and medical grounds.
In any event, a later amendment can overrule a previous one (as the 21st did) or anything in the actual body of the Constitution. Hence, had Congress not specifically exempted religious ceremonies in the Volstead Act, it *would* have trumped the First Amendment (vis-a-vis freedom of religion).
The Wolf