My wonderful husband got me an isi gourmet whip for Christmas and I decided it was time to play. I had co2 cartridges and grapes so I made carbonated grapes as my second experiment (I made whipped cream the day after Christmas but I can’t post those pictures). The secret to carbonated is…owning an isi whipping syphon. That and cold. Cold allows Co2 to get into food on a molecular level. No cold, no fizz. You need to chill both the whip and the grapes completely. Then you need to put in 2 Co2 cartridges being sure to hold down the handle to expel gas after the 1st cartridge but not the second. 
This gets rid of the air at the top of the canister so that it is completely filled with Co2. The Co2 must now make it’s way into the fruit so you refrigerate the whole thing on it’s side. Grapes take 8-10 hours to carbonate and last about 10 minutes so serve immediately. Once we expelled the gas and pulled them from the canister they were sizzling and whistling with co2. They taste almost like fermented grapes. We paired them with some Pt. Reyes blue cheese, but we immediately thought…sangria!
The Accidental Gastronomist 