There are many customs associated with Shavout, you can read about some here and here. One, is staying up all night and learning Torah (or at least part). This custom, which began in the 16th century in Safet spread rather quickly throughout the Jewish world. R. Yosef Karo, the author of the Shulkan Orakh lent a spiritual side. R. Karo stayed up all night and was studying with his student R. Shlomo Alkabtz (author of Lecha Dodi) and the following occurred:

Rav Yosef Karo and I agreed to stay up all night on Shavuot… we did not sleep for one minute… and when we began to study the Mishna.. we heard the voice of the Divine Presence, [with a feeble voice] speaking through Yosef Karo: ‘May you be blessed; return to your studies, do not stop for one minute, and go to Eretz Yisrael… Do not have pity on your vessels [material goods], because you will be sustained by “the upper realms”… so hurry to Eretz Yisrael, because I will be your sustainer, and I will provide for you and the peace of your house.’ And we all raised up a great cry of joy, when we heard the Divine Presence, her voice pleading with us…

Thus, feel the Divine and give Him honor.. and God will cause your hearts to merit becoming one with the Holy Land, to work it together, Amen.

Elliott Horowitz, who we had mentioned previously, has a rather interesting explanation to the quick spread of the custom. Horowitz notes that the rise in popularity of remaining up all night was due to the new drink – coffee. Coffee with its stimulant powers allowed more people to participate in this ritual. Thus, Horowitz notes in a period of thirty years no less than five editions of Tikkun lel Shavout are published in Venice. The same is true in other areas of Europe. This coincided with the rise of coffeehouses. Venice, the same city with all the printings of the Tikkun lel Shavout, in the 18th century, had some 200 coffeehouses (even prior to the rise of Starbucks). In Worms, the community was tasked with supplying coffee specifically for Shavout night. These facts precipitated greater parcipitation in a ritual with its demand upon wakefullness through the night.

While the above is rather interesting explaination for the spread of this custom, it is worth noting that Horowitz’s article appears incomplete. Specifically, he doesn’t touch on two other rituals which would benefit from coffee. The first would be Pesach night. As one is obligated to stay up (and this is min HaTorah) coffee it would seem would be perfect. (In fact, Briskers only stay up on Pesach night and do not stay up on Shavout to highlight this.)

But, perhaps coffee was not used on Pesach because a) it was a private – in the home and b) some considered hametz or kitnyot or at least susceptible to admixture with them.

The second area is the custom to say Shilchot at midnight. Many say it in the morning or some even say it early evening, but many hold midnight is the best time, why did this not benefit from coffee? In other words, why do we not see a rise in people reciting Selichot at midnight after coffee is introduced.

Finally, Horowitz does not discuss how almost all of the kabalistic customs from Safed where quickly adopted by the rest of Europe even when they had nothing to do with coffee. So the remaining awake all night can be seen as just an outgrowth of the acceptance of the others, think kabbalat shabbat etc.

Although Horowitz doesn’t touch upon these, his thesis is one to bear in mind when one is indulging in coffee (today RedBull) and cheesecake at 2 am.

Sources: Elliott Horowitz, “Coffee, Coffeehouses and the Nocturnal Rituals of Early Modern Jewry,” AJS Review 14:1 (Spring, 1989) 17-46; For a fascinating view of the spread of coffee to Amsterdam Jews and the rest of the world, one should read David Liss’s historical fiction work “The Coffee Trader.”