One cup of sauerkraut has 4 grams of fiber, per the USDA. Probiotics in the gut use fiber as fuel.
Kimchi, also fermented cabbage, is the spicy Korean cousin of sauerkraut. It can have scallions, radishes and shrimp added to give it more flavor.
Kefir is like drinkable yogurt. It's made when kefir grains, which are colonies of yeast and lactic acid bacteria, ferment the sugars in milk, giving it a slightly thicker consistency and tart flavor.
Kombucha is a tart, fizzy tea made by adding a SCOBY (symbiotic colony of bacteria and yeast) and sugar to green or black tea. It's then fermented for a week or more.
Miso is a fermented paste made from soybeans, barley or rice. Similar to other fermented foods, beneficial bacteria are produced in the fermentation process.
Tempeh is similar to tofu in that it's made from soybeans, but unlike tofu, tempeh is a fermented food, so it contains probiotics.