'Workaholics' Stars -- Invited to Live Porno Taping ... For Pimping XXX Site

The guys from "Workaholics" better give a big thank you to co-star Adam DeVine ... 'cause a porn site is offering to let them watch a smut session IN PERSON -- for giving it public props.

DeVine told Rolling Stone last week he has trouble writing at home because of Porn Hub ... adding, "they know what guys like" ... so the site reached out extending its open offer.

The letter says the company has partners who film close to the "Workaholics" set ... so Adam, Anders and Blake can cruise by anytime to check it out.