As with so many things each hospital gives different advice and, for each patient, the effects of things can be vastly different.
I am a sleever and am 13 months post surgery. I was given a lot of post op advice that was basically relevent to either bands or bypasses but not really for sleeves because, up to that point, they had not offered sleeves and hadn't written advice that was procedure specific!! In the end the nurse specialist at my hospital said they never tell people NOT to drink as she knows people still will she just asks that people are sensible with what they have and that they behave moderately!!
I tried fizzy water about 3 months post op and could manage it so had it occasionally. Then, in May last year, my nephew and his cousin had their 1st Holy Communion with a huge joint family celebration at the family restaurant - these affairs usually involve free flowing drinks especially cava/champagne and this occasion was no different. As I could tolerate the sparkling water (and had had fizzy soda's on occasions) I tried a glass of champagne which I managed so now I will have a glass or two at a celebration.
You would need to see if you tolerate it or not (try first with sparkling water as it's not going to have anything other than the carbonate in it so you will know if the fizz agrees with you or not!) and then decide if it's worth it for you. Remember as well that, for a lot of post-op patients, their tolerance to alcohol is majorly reduced in comparison to their previous habits!!
Tatiana