It often has additives such as citrus fruits, apples, berry juices, or artificial flavorings. Flavored kilju from fruits for example doesn't necessarily have to be sweet as long as all sugar is consumed by the yeast.
Kilju (15-17% ABV) contains 2.4-2.7 times more water than 40% distilled spirit. Since kilju contains approximately 85% water, it can be mixed with concentrates like a drink mixer, fruit syrup, or squash concentrate.