I love them. .....many people use them and if poor Spike doesn't have the intelligence to know to be careful with hot items regardless of a sleeve then maybe he/she needs to stick with colas.
Coffee sleeves are usually closed at the bottom, so the weight of the coffee keeps the cup in the sleeve. Very similar to a can cooler. One would have to be careful with hot coffee no matter what they were using. Hope this helps. I think it's a very cute idea!