Are there any special dietary laws or rules against smoking or drinking in Scientology?
No. There are no dietary laws whatsoever and no general prohibitions against smoking or drinking. However, Scientology does have a mandatory rule banning the consumption of any alcohol within 24 hours of or during an auditing session or training. The effects of alcohol would make it impossible to benefit from these religious services.
Smoking is forbidden in course rooms or during auditing sessions, since it would distract oneself and others.