When you don't have any insulin, your body goes into a state of diabetic keto-acidosis (DKA). While in this state, sugar builds up in your blood, but does not enter your cells. Your liver dumps glucose into the bloodstream which causes dehydration, as the kidneys work overtime to clean the blood. The body eventually uses an alternate metabolic pathway to produce energy which dumps byproducts into the blood which cause it to turn acidic among other things.
Speaking from experience, severe DKA is extremely uncomfortable. The problem is in your blood, so you feel a constant and extreme discomfort everywhere in the body, there's no body part that you can focus on where it isn't happening. You become extremely tired and lethargic and also irritable. You get angry and panicked and cognition slows down so you don't feel like yourself. You are very hungry and very thirsty but nothing you eat or drink alleviates the sensation. You also feel as though you cannot breathe enough to sate your body, so your breathing becomes faster and shallower.
It's difficult for me to imagine anything worse than dying of DKA. Maybe being lit on fire? That's short though, a death by DKA happens over hours or days. The cruelty here is spectacular.
Insulin is on the WHO essential medication list. The type of insulin that could alleviate these symptoms is cheap and widely available. There is absolutely no excuse here. Every doctor and nurse knows how to treat this and stop this kind of suffering.