Blood Sugar And Illness

My husband has had diabetes for 20 years. He watches his diet and exercises. He had some sugar-free cough drops for a sore throat. After taking one, he tested his sugar level, which was 263. He had an even higher level after drinking espresso with Splenda. He never has readings like that, even after eating carbs. Just wondering ? can being sick raise sugar? Or is it the artificial sweeteners?