Question: What is the name of this traditional Slavic and Baltic fermented beverage that is used for a flavor in Fruktime and commonly made from rye bread whose colour contributes to the resulting colour of the drink?

Context paragraphs:
Kvass: Kvass is a traditional Slavic and Baltic fermented beverage commonly made from rye bread, known in many Eastern European countries and especially in Russia as black bread.  The colour of the bread used contributes to the colour of the resulting drink.  It is classified as a non-alcoholic drink by Russian standards, as the alcohol content from fermentation is typically low (0.5–1.0%).  It may be flavoured with fruits such as strawberries and raisins, or with herbs such as mint.

Rugbrød: Rugbrød (] ) (Danish style rye bread) is a very common bread in Denmark.  "Rugbrød" usually resembles a long brown extruded rectangle, no more than 12 cm high, and 30–35 cm wide, dependent upon the bread pan in which it is baked.  The ingredients typically include rye flour, cracked or chopped rye kernels and seeds such as sunflower seeds, linseeds or pumpkin seeds.  Sourdough is almost always the base because commercial yeasts are unsuitable.  The naturally fermented dough will develop a naturally occurring "Lactobacillus" culture in symbiotic combination with naturally present yeasts.  It is essential in baking rye-based breads because the chemistry of rye flour produces an environment that is acidic.  The most commonly present yeast species in the production of naturally leavened dough is "Saccharomyces exiguus", which is more acid-tolerant than commercially produced "S. cerevisiae", although the latter and other strains may also be present.  Research has shown that when creating a naturally fermented starter, any naturally present "S. cerevisiae" will have died off after a few days.

Brottrunk: Brottrunk (literally meaning "bread drink" in German) is a fermented grain beverage similar to bread kvass, made in Germany from bread.  The bread is baked from biodynamically grown grains.  This bread is then fermented in a proprietary month-long process.  Then, without further processing, the liquid is bottled.  First marketed in 1981 by master baker Wilhelm Kanne, this non-alcoholic probiotic beverage is distributed as "Kanne Brottrunk" in Germany and in several European countries.

Boza: Boza, also bosa (from Turkish: "boza" ), is a popular fermented beverage in Kazakhstan, Turkey, Kyrgyzstan, Albania, Bulgaria, Macedonia, Montenegro, Bosnia and Herzegovina, Azerbaijan and other parts of the Caucasus, Uzbekistan and Romania, Serbia.  It is a malt drink made from maize (corn) and wheat in Albania, fermented wheat in Turkey, and wheat or millet in Bulgaria and Romania.  In Egypt where it is known as "būẓa" (بوظة ) it is usually made from barley.  It has a thick consistency, a low alcohol content (around 1%), and a slightly acidic sweet flavor.

Tequila, Jalisco: Santiago de Tequila (    ; Nahuatl: "Tequillan, Tecuila" "place of tribute") is a Mexican town and municipality located in the state of Jalisco about 60 km from the city of Guadalajara.  Tequila is best known as being the birthplace of the drink that bears its name, “tequila,” which is made from the blue agave plant, native to this area.  The heart of the plant contains sugars and had been used by native peoples here to make a fermented drink.  After the Spanish arrived, they took this fermented beverage and distilled it, producing the tequila known today.  The popularity of the drink and the history behind it has made the town and the area surrounding it a World Heritage Site.  It was also named a "Pueblo Mágico" (Magical Town) in 2003 by the Mexican federal government.  Tequila has also been famous for being the prime setting in the successful Televisa telenovela "Destilando Amor", starring Angélica Rivera and Eduardo Yáñez.

Tepache: Tepache is a fermented beverage made from the peel and the rind of pineapples, and is sweetened either with "piloncillo" or brown sugar, seasoned with powdered cinnamon, and served cold.  Though tepache is fermented for several days, the resulting drink does not contain much alcohol.  In Mexican culinary practice, the alcoholic content of tepache may be increased with a small amount of beer.

Estonian cuisine: Traditional Estonian cuisine has substantially been based on meat and potatoes, and on fish in coastal and lakeside areas, but now bears influence from many other cuisines, including a variety of international foods and dishes, with a number of contributions from the traditions of nearby countries.  Scandinavian, German, Russian Latvian, Lithuanian and other influences have played their part.  The most typical foods in Estonia have been rye bread, pork, potatoes and dairy products. Estonian eating habits have historically been closely linked to the seasons.  In terms of staples, Estonia belongs firmly to the beer, vodka, rye bread and pork "belt" of Europe.

Fruktime: Fruktime - a series of the carbonated soft drinks which are on sale in Russia and Ukraine, distribtuted by The Coca-Cola Company.  It is made in various flavouring variants: Buratino (caramel), Tarhun (tarragon), Hand bell, Lemonade, Pear, Strawberry, Apple, Cream soda, Kvass, and Baikal (Natural).

Rye bread: Rye bread is a type of bread made with various proportions of flour from rye grain.  It can be light or dark in color, depending on the type of flour used and the addition of coloring agents, and is typically denser than bread made from wheat flour.  It is higher in fibre than white bread and is often darker in color and stronger in flavor.

Rupjmaizes kārtojums: Rupjmaizes kartojums is a traditional Latvian dessert based on the country's famous traditional dark rye bread.  Rupjmaizes kartojums is similar in appearance and construction to the trifle of the British Isles, and is often called Sweet Rye Trifle, or Latvian Ambrosia among English speakers.  It uses Rupjmaize dark rye bread rather than sponge cake.  Rupjmaizes kartojums is an iconic Latvian food, and is considered a treasure of the national cuisine.  It was the sweet chosen to represent Latvia in the Café Europe initiative of the Austrian presidency of the European Union, on Europe Day 2006.

Supporting paragraphs: Fruktime Kvass
Answer: Kvass