It is according to one study the nicotine in tobacco that can increase blood sugars as vape liquids usually have nicotine in them they will also affect blood sugar levels so they are ok for short term use if being used to stop smoking but in the long term would be not much different to smoking.
"March 28, 2011 (Anaheim, Calif.) -- Nicotine appears to be the main culprit responsible for high blood sugar levels in smokers with diabetes, according to new research presented here at the annual meeting of the American Chemical Society."
''If you have diabetes and if you are a smoker, you should be concerned about this," says Xiao-Chuan Liu, PhD, a researcher at California State Polytechnic University in Pomona, who spoke about his findings at a news conference Sunday.
In his laboratory study, he exposed human blood samples to nicotine. The nicotine raised the level of hemoglobin A1c, a measure of blood sugar control. The higher the nicotine dose, the more the A1c level rose.
For years, doctors have known that smokers who have diabetes tend to have poorer blood sugar control than nonsmokers with diabetes.
However, until Liu's study, he says, no one could say for sure which of the more than 4,000 chemicals in cigarette smoke was responsible"
https://www.webmd.com/diabetes/news/20110328/nicotine-and-blood-sugar-bad-combination#1