If you're in the USA, Chobani full fat and Oui by Yoplait are ok, but there's added sugar. Whipping it with a whisk or handmixer will make it more like a mousse texture. There's a decent weight gain powder made with pea protein, Orgain that has probiotics. It says use water to mix with, but I use whole milk. If you're not trying to gain, water is probably fine , if you are trying to gain, add a dollop of peanut or almond butter.
Refrigerated sauerkraut has probiotics, but I don't care for it.