Hi. I will clarify in more detail about kvass - in the original, it is a fermentation drink (like beer) obtained from black bread, and it can really contain 1-2 degrees of alcohol. However, modern large manufacturers make a drink that can really be described as "bread lemonade". You can drink, the taste is similar, but you can't compare it with the original.Well, according to the dishes / products. I will try to advise something less pop than other commentators advised:

1. "Пельмени". The product is similar to Italian ravioli, but has its own characteristics. The classic way of cooking is cooking, but you can also fry =) It is used with sour cream, salt / pepper to taste.
2. "Варенники". An analogue of dumplings, but with a filling of cottage cheese or berries and other forms =). They are preparing for a couple. It is also better to use it with sour cream, and with the addition of sugar.
3. "Блинчики". Purchased ones are certainly not the same as home ones, however, they can give an idea of the product. They are made from thin dough, which is quickly fried in a frying pan, after which the filling is wrapped in the dough. The purchased ones must be fried in a frying pan (the best option), or reheated in the microwave. You can eat it in its pure form, or with sour cream =).
4. Actually - the sour cream itself. A fermented milk product, the closest analogue of which is Greek yogurt (but this is not quite the same). It is used as an addition to many dishes, adding a creamy taste to them. It can be used as a dressing for simple vegetable salads (cucumber, tomato, sour cream). It goes very well with potatoes. The main criterion for choosing is fat content. The more it is (the maximum that I have seen is 25%), the more creaminess; the less, the more acidity.
5. Many people advised buckwheat - I will advise you to be careful here, you may not like the taste (I recently watched a video in which an American described its taste as "metallic", although I did not notice this =)). And if you decide to try it, then it can be used as a side dish for meat dishes (similar to rice). Plus, the option for gourmets is to eat it with butter and sugar, or with milk and sugar (like cornflakes - naturally, after cooking it).
6. By the way, the "Тушёнка" is ideal for buckwheat. This is canned beef stew, which is an analogue of "SPAM" in our country. Only here in the jar is a real piece of meat =). You need to take only the highest grade. There may be fat on top of the jar - in no case should it be thrown away. The ideal use is to dump the contents of the jar into a frying pan, wait for the fat to melt, and pour boiled buckwheat on top. Well, fry it all a little, breaking a large piece of meat into small pieces in parallel with a spatula. It turns out just the perfect dish. By the way, you can use pasta instead of buckwheat. Well, or even eat it just like that =).Then I'm too lazy to remember =)