Promethazine
"Promethazine was prescribed twice to me for mild sedation by my neurological doctor. I tried in in doses between 10mg  and higher. This doesn't make me drowsy unless I'd had pain also and taken  an opioid with it. The only effect I received was the taste of it. The second time it was given to me instead of zopiclone. Still, no effect.
I tried it once as a treatment for nausea; 40mg. didn`t work."