The phrase "unsweetened yogurt" refers to yogurt that doesn't have any added sugar or sweeteners. It is plain and doesn't taste sweet.
Sentences with «unsweetened yogurt»
Mix a cup of unsweetened yogurt with strawberries and top it off with chopped mint. (zenbellyblog.com)
My daughter will eat plain unsweetened yogurt quite happily too. (easynaturalfood.com)
The taste of unsweetened yogurt can take some getting used to, I have found that many patients find it too bitter or «acidic» at first. (ericbakker.com)