Instead of yogies, I use the tiny little dark chocolate chips... no more than one a day. Usually they only get a couple a week. Still just as nutritionally void, but the chocolate helps a little with the myco flare-ups.
Myco is short for mycoplasma (again, my spelling is generally awful), which is an infection that all pet rats have. When a rat is stressed, immuno-compromised, or something similar, the infection can 'flare' leading to respiratory issues.