I've made these as fully-submerged mason jar eggs a few times now: https://anovaculinary.com/easy-homemade-sous-vide-egg-bites/

little 4 oz jarz are perfect for 2 eggs.

The fingertip tight allows air to bubble out but water doesn't seem to get in. (it's extra cool because they actually form a little vacuum seal too)

I suspect yogurt would behave the same way - but who knows?! It's always an experiment the firs time.