Estonian cuisine generally is a mixture of different cuisines, mostly Russian. Which is why pure Estonian cuisine doesn't generally have many worldwide known dishes.

Ingredients
for 6 people
400 g of rye bread (the harder it is, the better and thicker the soup will be)
1.5 L of water
2 dl of raisins (optional, but recommended for authenticity. You may also replace them with apples)
1-1.5 dl of sugar
0.5 tsp of cinnamon
2 dl of cranberry juice or some other sour juice
For serving: Milk or whipped cream (optional)
Preparation
Slice the bread and soak in the water in a bigger pot until it's softer. Then boil the same bread with same water until it's all mushy. Strain the mixture through a sieve and place the puree back into the pot. Add juice, raisins/apples, cinnamon and sugar and mix. Boil again and let it simmer for few minutes.
Serving: Let it cool down, place a portion in a bowl and add some milk or whipped cream.
NB! This recipe will make a slightly watery soup. If you want a thicker consistency, then use about 1 l of water. When the soup cools down, it'll thicken either way.
See this recipe for more information:
Picture from nami-nami.ee