We preserve a lot of compotes because the winter here is relatively long and it is not always easy to get fresh juices or fruits. In addition, this is a good storage method - if a lot of apples were born in a certain year, then you can put them on compotes and drink them safely for a couple of years (if you store them in a cold cellar or refrigerator, canned in jars).
A kvass recipe usually consists of something rye - rye flour, or rye bread, or even rye grain. The second component is yeast, the third is sugar. All this is simply mixed with water and stands for two or three days at normal, room temperature (but not in extreme heat).
Frankly, I won’t risk voicing the recipe for good kvass, because it’s not always easy to make, and I’m a rather lazy person and just buy rye concentrate. I dilute it with water, add sugar and yeast, and after 2-3 days I get kvass. Moreover, I would not say that this kvass is ideal - it is rather some simple and cheap drink that is not so bad to drink just water, but not so good to make it for years every day.
If you can’t find a recipe in English using a search engine, try using an online translator, type in the word kvass, and search. To make this action easier for you, I looked for recipes, but they are in Russian. They can be translated automatically (if I'm not mistaken, the right mouse button in the browser), and in principle there is nothing abstruse or complicated there. The only thing is which recipe is good or bad, I won’t undertake to decide, because I don’t understand this issue well - I will advise the recipe, but some nasty muck will turn out. Therefore, I will not take responsibility)) Frankly, when I first made kvass, I really got disgusting that you can’t drink, and I had to redo everything four times before I got a completely tolerable drink that was not dangerous to health. Making kvass, like making beer, requires some experience and skill. Which I don't have.
https://1000.menu/catalog/kvas
They also make a slightly strange dish called “okroshka” from kvass, something in between a salad and a cold soup, but, to be honest, I don’t eat it at all. My parents love it, but I don't, and I don't understand how i can eat it at all 
As for sugar, in Russia society is split into two warring camps - some argue that sugar is very harmful, others - that sugar, on the contrary, is very useful. The second camp is more aggressive, to the point that they can start swearing if they start to prove that they can’t eat sugar. There are probably 3 factors here:
1. During the collapse of the USSR, there were serious problems with food shortages. In those days, we were greatly helped (by the way) by American humanitarian aid, as well as huge chicken legs, which went practically for next to nothing. Well, at this time, sugar, which was extremely scarce and expensive, began to be declared unhealthy. And the people who used it began to perceive these things as an attempt to deceive themselves and leave them hungry and poor. Therefore, to tell them that sugar is harmful is the surest way to make them very angry. 
2. For some reason, some Russians have no susceptibility to harmful products at all. For example, my grandfather, who, as a war veteran, received many expensive food packages from the state (which included black caviar, good sausage, and yes, sugar in very large quantities), after the hungry years of the war, he ate a lot of sugar. He actually ate about 2 kg of sugar a day, and when he died at 97, he never developed diabetes. I don't know, maybe it's some kind of genetic mutation, but some Russians can eat as much sugar as would make a normal person feel at least unwell. Frankly, I have the same situation, although in principle I am overweight - I weigh 125 kilograms. True, I differ from ordinary fat people in that I lead a fairly active lifestyle, constantly carry some kind of weight and walk kilometers with a herd through the hills, where you have to not only walk, but also climb. Often I collect stones in bags there, and bring these bags loaded with stones home, it happens that I carry 80 kg of stones in a bag on my shoulders for several kilometers, because my mother wanted to make a flower bed out of stones, and I have money to buy stones no, because I'm lazy and too lazy to work for money.
Ah, well, yes, I don’t eat much less sugar than my late grandfather, but at the same time I don’t have diabetes and it looks like I won’t.
3. Sugar substitutes sold in Russia are extremely unhealthy. They are of extremely poor quality and are produced for the most part not by the food industry, but by the chemical industry. As a result, the people who used them got a number of health problems, and after that, the rest, looking at them, on the contrary, began to eat even more sugar. It got to the point that after replacing sugar with a substitute in soda water, they stopped buying it!
And it turned out that sugar becomes more expensive and becomes some kind of elite product, they buy it, stock it up, and swear if they try to give something else instead of it. The only respected sweetener here is only bee honey. It is also eaten a lot, and active sales are going on, it has come to the point that some people have quit working, left the city, breed bees and live in the honey trade.
Therefore, if you go into the recipes of many canned Russian cuisine, you will see sugar everywhere, even in cucumbers. There is not so much of it there that they are sweet, but it is customary to add it there. 50 g per 3 liter jar.
Moreover, Russian sugar is made from a beet variety, and it is much sweeter than cane Cuban. Although, of course, many of the Russian people will eat all their Russian sugar and buy cane sugar in Cuba, and they will also eat it.
Well, it's easy to guess which camp I belong to regarding sugar 

If I now count how much sugar I have in my house, it will come out at least 500 kilograms. Moreover, it was bought both at retail in stores and in bulk, in 40 kg bags.
The final touch to this picture can be voiced by the fact that there is not a single recipe for kvass without sugar. Kvass without sugar is impossible, yeast will not work without sugar.
In general, everything can be defeated in Russia - drug addiction, drunkenness, infidelity of wives or husbands, but sugar is invincible. Here I can remember my grandmother, who once ate 3 liters of jam in one day, and in Russian jam sugar goes in a ratio of 2 to 1, 2 parts of sugar and only one berry.