What do I substitute for Greek yogurt in a pizza dough?
You can make your own version of Greek yogurt and it will be even better than what you buy in the stores.  What you need to do is buy "plain unflavored yogurt", preferably full fat or whole milk.  Then get a cheese cloth, and put the yogurt into the cheese cloth that is covering a bowl (please make sure the cheese cloth or a very thin cotton type wash cloth not (like a bath towel) but very smooth like a bed sheet, is secured over a bowl so that the yogurt can drain and the cloth will stay in place. It will take an hour or maybe two or even three, but the water will come out of the yogurt and it will be thicker and richer.  I think the water that comes out is called whey.  Preferably buy a middle eastern brand of yogurt, or an Armenian or even Russian brand.  There is something different in those brands that tastes a little bit better, especially if you get the water out, Mountain High is also good.  You can also buy something called "lebni" but that is a different product of yogurt, similar process, but if you try what I say, it will work fine.  If you do this with nonfat or lowfat, it is ok also, but we prefer the whole milk style and my friends and family do not like the Greek yogurt at all.  Funny, my Greek friends don't care for Greek yogurt either. We find Greek yogurt has more of a cloudy taste rather than a crispier creamier fresher taste and not so heavy and old as Greek yogurt.  Good Luck