Kykeon (Barley Water)

The Greeks also drank kykeon (κυκεών, from κυκάω kykaō, "to shake, to mix"), which was both a beverage and a meal. It was a barley gruel, to which water and herbs were added. In the Iliad, the beverage also contained grated goat cheese. In the Odyssey, Circe adds honey and a magic potion to it. In the Homeric Hymn to Demeter, the goddess refuses red wine but accepts a kykeon made of water, flour, and pennyroyal. Greek practice was to dry the barley groats (whole grains with the husks removed) and roast them before preparing the porridge, according to Pliny the Elder's Natural History (xviii. 72). This produces malt that soon ferments and becomes slightly alcoholic.

Used as a ritual beverage in the Eleusinian Mysteries, it was also a popular beverage, especially in the countryside: Theophrastus, in his Characters, describes a boorish peasant as having drunk much kykeon and inconveniencing the Assembly with his bad breath. It also had a reputation as a good digestive, and as such, in Peace, Hermes recommends it to the main character who has eaten too much dried fruit.

In the time of the Roman Empire Kykeon was still a popular drink made from water, wine, honey and barley with various herbs added to individual taste.

Ancient Greek Pulp - (Arxaios hylos Kikeon)

Kikeon is something between food and drink. The word “kikeon” (eoea?i) comes from the verb “kikan” (eoeUi), which means thickening by continuously stirring. The recipe that is given best resembles the ancient version of “Kikeon.”

From Homer's Iliad, II 638 - 41:

As written in Homer's The Iliad, Hecamede, daughter of Arsinous, was captured from the isle of Tenedos and given as captive to King Nestor. Described as "skilled as a goddess", "fair" and "proud", Hecamede was not a concubine but a serving woman. In her most prolonged mention she serves Nestor and Prince Machaon Pramnian wine, a medicinal drink.

Homer Iliad Book 11

Fair-haired Hecamede
made them a soothing drink. Old Nestor had taken her
from Tenedos, when Achilles ransacked the place.
Daughter of great-hearted Arsinous, she'd been chosen
for him by the Achaeans, because he excelled them all
in giving wise advice. First, she pushed out in front of them
a well-polished table with feet of blue enamel.
Then she set there a bronze basket holding onions,
to add spice to their drink, with pale honey and bread
made of sacred barley. Beside these she set a cup,
a magnificent work Nestor had brought from home,
studded with gold. There were four handles on it,
around each one a pair of golden doves was feeding.
Below were two supports. When that cup was full,
another man could hardly lift it from the table,
but, old as he was, Nestor picked it up with ease.
In this cup Hecamede, looking like a goddess,
made a soothing drink for them from Pramnian wine.
In it she shredded goat's cheese with a grater made of bronze,
then shook white barley grain on top. When she'd prepared it,
she invited them to drink.

To make this after some experimentation, Sally Grainger takes her cue from Cato:

85. Recipe for Punic porridge: Soak a pound of groats in water until it is quite soft. Pour it into a clean bowl, add 3 pounds of fresh cheese, 1/2 pound of honey, and 1 egg, and mix the whole thoroughly; turn into a new pot.

3/4 cup (120 gr) semolina
375 gr riccota cheese
2 spoons honey
1 small beaten egg

Soak the semolina for 10 - 15 minutes in plenty of water, enough to cover it. When it softens, strain it and add the ricotta cheese, the honey and the beaten egg. Heat the mixture in low temperature and do not let it boil.