Rinse the grains and cook in the 8 cups water until very soft. Press through a fine sieve; discard coarse solids.
Cool the strained base. Mix yeast, the tablespoon of sugar, and lukewarm water, then whisk into the base.
Cover and ferment in a cool place, stirring occasionally, for up to 24 hours; warm conditions shorten this substantially.
Fermentation disclaimer: This original home recipe has not been validated for food safety. Its time-only instructions do not establish safe fermentation: elapsed time, bubbling, sourness, smell and taste are not proof of safety. Do not use this recipe as a validated fermentation protocol; seek a tested process and qualified food-safety guidance before preparing it. Refrigeration does not make an unsafe batch safe. Fermentation can produce alcohol, so this drink is not guaranteed alcohol-free. Bulgur contains wheat and gluten. Commercially prepared boza is an alternative.
Stir in sugar and water gradually to a thick, pourable consistency. Chill, then serve with cinnamon and leblebi. Refrigerate and consume within a few days.
A warm spice infusion with galangal, ginger, cinnamon and cloves, topped with walnuts. In Adana, kaynar is associated with visits celebrating a new baby. That cultural association does not establish a medical or lactation benefit; this is a culinary serving recipe.