Best to see a doc first for a diagnosis, and then treat yourself as you see fit.
The fastest way pun intended is fasting. You need to avoid fruit juice its fructose not much different to High fructose corn syrup which is virtually in all processed foods as a cheap sweetener, all 0 calorie sweetener will create an insulin response, you body doesn’t deal with that well. Alcohol as well as its poison for your liver.
Complex carbs are better but not much you get about another 20 minutes of digestion before its converted to glucose. I am atm reducing my carbs and doing intermittent fasting, I only eat 2 meals a day between 5pm and 7 pm. Improves insulin sensitivity, allows your body to repair it self as up to 80% of the energy you use is digesting food. Also when you eat all your calories in a short space of time you only have to produce insulin once to move the glucose into your cells if you are not burning them up.
Once you got a diagnosis and if its insulin resistance check out this Doctor on Youtube, he has all the info you will need to do naturally through diet.
https://www.youtube.com/watch?v=_BloJpvdFXI