Viili is a Finnish fermented dairy product that is similar to yogurt. Due to its unique texture and taste, there are not many exact synonyms for viili. However, there are some alternative dairy products that are similar in some ways. For example, kefir, skyr, and labneh are all fermented dairy products that are similar to yogurt, but with different textures and flavors. Quark, a German dairy product, is also similar to viili, as it is a creamy and tangy dairy product that can be eaten on its own or used as a substitute for sour cream or cream cheese. Ultimately, while there may not be a perfect synonym for viili, these alternatives are worth trying for those who enjoy fermented dairy products.