During the manufacturing process, CO2 is usually pressurized to dissolve in these drinks to generate carbonic acid.
dˈʊɹɹɪŋ ðə mˌænjuːfˈæktʃɚɹɪŋ pɹˈɑːsɛs, sˌiːˈoʊ tˈuː ɪz jˈuːʒuːəli pɹˈɛʃɚɹˌaɪzd tə dɪsˈɑːlv ɪn ðiːz dɹˈɪŋks tə dʒˈɛnɚɹˌeɪt kɑːɹbˈɑːnɪk ˈæsɪd.