I was halfway serious, over the counter diphenhydramine IS the same as prescription diphenhydramine... but yeah you could use Nyquil too. Or some liquor
hands down worst substance i ever tried, when i was a teenager i took a lot to try to get high and had the worst time of my life. If you REALLY want to have a good buzz, stay away from Diphenhydramine and use Doxylamine instead.
It is said that dyphen potentiates methaqualone. Sopors and mandrax were formularies of methaqualone and dyphen. I recently read a paper written in the 80's that refuted the claim and practice but i found that mandrax had a different, more powerful and more dreamy effect where rohers could actually be speedy in comparison.