Agree on the Greek yoghurt taste. I'd sweeten it with banana, as it can mix nice without much effort and is also packed with nutrients along with only a tiny bit lethal radiation. Calories I've no idea about though.
I've often wondered why grocery stores are infested with flavored yogurts, especially when they are often out of the plain variants that I'm seeking. I've thankfully never felt the need to 'flavor' yogurt and prefer its taste unadulterated - sourer the better.