شرب الدخان ممنوع
SHurbu Ad Dukh KHaan Mam nOO'
kh=ch in scotch loch

this sentence is literlay : drinking (Arab uses drink to describe the act of smoking)cigarettes is forbidden.

The most Common all over Arab countries is
ممنوع التدخين
ممنوع Mam Noo' means forbidden
التدخين At Tad Kheen means smoking
but the grammatically correct way is to say التدخين ممنوع