A refreshing nutritious drink, good for winter and summer. The name survives in Egypt to this day to designate comparable drinks; it is especially popular during the month of Ramadan.
Subiya is sweetened grain-based digestive beer, a variety of what was called fuqqāʿ in medieval times. It was said to be popular in Egypt. The best was said to be the variety made with rice. The book of Kanz offers six recipes, two of which are made with rice; the rest are made with bread and with flour cooked into thick porridge and then used to make the drink.
The prepared liquid was kept in jars overnight to ferment a little, or for a day or two and perhaps a little longer but not more than five days. It was said to be useful for the digestion, and with the addition of spices, it could be aphrodisiac. From Edward Lane’s Account of Manners and Customs of the Modern Egyptians, p. 324, we also learn that subiya was made with melon seeds, which I assume were dried and toasted first before using them crushed as this would have brought out their enticing aroma. He says subiya was sold in the streets of nineteenth-century Cairo.
In today’s Egypt, sūbiya is still popular, especially in the fasting month of Ramadan. Professionals make it with crushed barley and bread broken into pieces, drenched in water and left to ferment for a couple of days. It is strained, and the resulting liquid is spiced with cinnamon and cardamom and sweetened with sugar. After setting it aside for a day, it is good to drink, chilled. There are also home recipes using rice flour.
Check out this link, for instance (it is in Arabic, but google translator will help in figuring out its contents).
In the book of Kanz recipes 429–34 all deal with this sort of drink. Here is one of them which I have tried and liked:
Subiya Recipe 430, makes 4 servings
5 slices of a plain white loaf of bread
5 cups warm water
A sprig of parsley
¼ teaspoon crushed cardamom
A stick of cinnamon
Optional: a few tender citron leaves, washed; a sprig of tarragon, and a sprig of mint
Put the pieces of bread in a bowl along with the water. Set aside for about 30 minutes to allow the bread to soften. Mash the mix with your fingers, and strain it through a fine-meshed sieve.
Pour the resulting liquid into a container with a lid. Add parsley, cardamom, cinnamon stick, and the optional ingredients, if used. Cover the container, and set it aside for a day or two at room temperature. Strain it again, and use it chilled with ice cubes, and sweetened to taste.