The flavored yogurts usually have a lot of extra sugar and/or chemicals. I don't like to give my girls anything containing sugar - only the natural sugars from fruits and veggies. I give them plain Greek yogurt every Sunday.
If that is what is on sale this week, great. Especially if you stretch it by adding layer ration. What I like to do is use a few spoonfuls of store bought yogurt in a slurry of milk and feed. Let sit overnight, and the cultures multiply.
Just know the little buggers can be picky. We had some leftover pumpkin egg nog. I offered it to them and they SNIFFED it first, refused to even taste it! Apparently certain spices have a strong smell they dislike. Mine do not mind vanilla but you might want to ask YOUR chickens!