Drinking one 12oz (336ml) serving of sugar-sweetened soft drink per day can be enough to increase the risk of type 2 diabetes by 22%.
It’s not possible to mitigate this risk by consuming artificially sweetened soft drinks either as these are also associated with increased risk of type 2 diabetes!
Naturally sweetened drinks such as juices and nectars do affect blood sugar levels so its probably best to water these down or make flavoured water by using pieces if fruit. This method contains alot less sugar than drinking juice or nectar.
The InterAct consortium. Consumption of sweet beverages and type 2 diabetes incidence in European adults: results from EPIC-InterAct. Diabetologia, 2013 (in press) DOI: 10.1007/s00125-013-2899-8