https://doi.org/10.1371/journal.pmed.1003950.s002
Figure C: Cancer risk associated with the combined exposure to artificial sweetener and sugar intakes, NutriNet -Santé cohort, France, 2009-2021 (n=102,865)
For me the two interesting cases are:
"Sugar above nutritional guidelines" and "no artificial sweetener" => 1.09 (0.97 - 1.22) P=0.158
"Sugar below nutritional guidelines" and "high artificial sweetener" => 1.12 (1.00-1.25) P=0.046
nutritional guidelines are 10% max energy intake from sugar, about 50 gram of sugar per day for a 2000 kCal diet (62 gram for 2500 kCal for adult male).
A 330ml coke can has 35g of sugar, so we're talking one or two max per day to keep below the guideline.
If I read this correctly if one makes the switch from sugary beverage to artificial sweetened ones and it lowers your total sugar intake below the dieteray guidelines then your relative risk factor doesn't change (at about +10% vs low sugar and no articial sweetener).