If you want less tart frozen yogurt without too much added sugar, try starting out with milder yogurt. Instead of Greek yogurt, try regular plain yogurt. Or choose lactose-free yogurt, which tastes sweeter. Dairy-free yogurt alternative may also be milder in taste. You can also neutralize the tart flavor by adding 1/8 to 1/4 teaspoon of baking soda to the mixture.