From what I've read, tea and coffee were introduced to Europe in the 17th century (coffee slightly later than tea). This was decades before the "beginning" of the Enlightenment, so I'm guessing superstitions and fear of things not fully understood were still widespread.
If a drink were suddenly introduced giving consumers a burst of focus and energy, then wouldn't it be rejected as "magic" or something similar?
I cannot say what the Europeans thought, however, I thought I met tell you what the Muslims thought. When tea and coffee were introduced to the Muslim world, they were enjoyed by the people and coffee houses formed to serve the beverages. But, in the 17th century, an Ottoman Ruler (can't remember his name exactly), banned coffee because of its stimulating effects on people. Also, it was linked with political rebellion in Europe. In addition, one motive for banning it was the addictiveness of coffee. The Qu'ran bans things like drinking alcohol because it is addicting and therefore is bad; similar logic applied to coffee. (not entirely certain about the addicting part. Can someone confirm?)