Do not use yeast only — you'll get a beverage with a much higher level of alcohol and unpleasant aroma (been there done that!). Start making your kvass when you have 1-to-3 days old dough in your refrigerator. The sediment on the bottom of the jar where kvass was fermenting can be used as a kvass starter. It is not safe to use it for more than 2 to 3 batches. Have your next kvass bread extract ready when your currently fermenting kvass is ready to be bottled.
A good seal is needed to withstand the bottle's pressure build-up that gives the beer its carbonation. I use flip-top beer bottles. The rubber seal of flip-top bottles can't hold the pressure over long periods. They are good enough to condition kvass for a few days, easy to clean, and you will never lose the flip-top. The rubber seals can be replaced over time. These bottles are cheap and easy to find. For a couple of bottles, look for good deals online or in Home Goods/TJ Maxx/Marshals/Hobby Lobby, etc. Since kvass is conditioned for a relatively short time, dark glass is not important.
My favorite sugar and flavoring ingredient is D-180 Candi Syrup. It can be found in many beer brewing supplies stores.
