What would these be? I'm fairly good at recognising people that are wasted on alcohol; the slurring, the weird sort of honesty and imbalance when they walk. And for one or two reasons I can spot an alcoholic who is hiding it well; a functional alcoholic, if you will.
But with coke what would it be? I suspect this of someone close to me but don't necessarily want to make any judgements as such just yet. When someone is drunk it's easy to spot but I'm not aware of what someone off their face on coke would necessarily be like, speaking very fast and rubbing their nose a lot?