I can tell you its not a good idea. I didn’t eat sweets to excess, my downfall was fruit and carbs. Anyway, the course is not a good one. I don’t want to scare you but it sounds like he’s not taking it seriously.

I suggest you read up on diabetes complications and if you do the cooking modify the diet you or he prepares by changing it at the front lines (the grocery store). I’m telling you its not worth what ever he is doing to keep hurting himself. I don’t want you to have a rude awakening, but this will most def. progress if he does not change his lifestyle. I recently changed diet to be low carb and low sugar. I’m consuming fruits low in sugar, strawberry’s, watermelon, peaches, etc. He could drink Orange juice to bring his sugars up IE: insulin. Start going for walks (if you don’t). I miss that terribly. I used to walk with my husband every day and I cannot now due to neuropathy. It affects the entire body. It can really mess with you. He should get an eye exam for diabetics too. Check cholesterol. He needs to see the doctor and listen to what they say. If he does not and refuses your imposing a better diet on him, then prepare yourself for the worst, because diabetes is a powder keg. Stay strong. Rely on this group for help. Your personal doctor. He can’t keep doing the same thing expecting different results. You both need support. IMHO.
Take Care and Be well, Nemo1