Yes. The World Cancer Research Fund commissioned a comprehensive review of cancer risk factors, signed off on by dozens of prominent scientists. They came up with ten key recommendations. One of them is, "Limit red meat and avoid processed meat." Another is, "Avoid high-calorie foods and sugary drinks." A third is, "Keep [body] weight low within the healthy range." Sugary drinks and obesity as risks for cancer are definitely well within mainstream science.
Doesn't "carcinogen" mean something a little stronger than "may increase risk of cancer"? Like I wouldn't call walking on the street a deadly activity just because it may increase your chance of death.
I didn't mention obesity, which is definitely a risk factor.
Sugar is only partially correlated with obesity, and I have never seen anything implicating sugar itself with cancer outside of paleo / bro-science circles. Plenty of people drink multiple sugary drinks daily for decades without getting obese. Warren Buffet is a good example. So is most the population of Japan.
https://www.wcrf.org/int/research-we-fund/our-cancer-prevent... (currently "down for maintenance", but available in gcache)