Kombucha can help promote healthy digestion, thanks to the live cultures floating around in there. The tea is fermented with the help of a SCOBY, which is basically a gooey bacteria culture that also boosts your microbiome, the key to health and probably happiness. Kombucha companies ferment and bottle their own stuff in big batches, and the whole process takes time, effort, and a healthy SCOBY (that's just fun to say) -- not to mention the tea component, which gets its own processing -- so you're better off just relying on the pros.
This is the refrigerated version, not the stringy canned kind your parents used to buy for Reubens, which your parents definitely did. Like kombucha, real sauerkraut is also fermented using friendly bacteria, once again helping out your digestion and microbiome. If you haven't gathered this, any naturally fermented product that provides you bacteria is going to be good for your gut, so buy a bunch of fermented goods and let them work their probiotic magic on you.