Is there a drink in Italy similar to kvass? Kvass is a low alcoholic drink made of (usually rye) bread. Is there something similar in Italy (like malt beer in Germany)? Or maybe is it possible to buy kvass in big supermarkets?
Your best bet is likely to be a Russian/Eastern European store. There are some in many larger Italian cities, search for "negozio russo" or "alimentari russo" in an area you are interested in. Some possibilities:

Rome


"Kozak" - Via dei Conciatori, 1c
"Galychnya" - Via Santa Maria delle Fornaci, 6


Verona


"Il Negozio Tipico Russo", Via Vincenzo Cabianca, 10


Cagliari


"Алёнушка" - via Francesco Carrara, 22


Genoa


"Angolo dell'Est" Vicolo Canneto il Curto


Carpi


"Europa-Est" - via Trento Trieste 34/a


It may pay to call ahead to see if they carry Kvass, if you can find a phone number.