Sicilian fast food
If you go to Italy, you must forget about eating at fast food "restaurant" chains like McDonalds.
If you visit Siciliy, it is almost a crime to eat at a fast food "restaurant".
The reason for this is that food gets better, the further South you go, the better the food (not only my opinion, even Italians from the North seem to agree). Catania is obviously no exception. I can understand that sometimes you don't feel like sitting down at a Restaurant or maybe you are just on a tight budget, but that is no excuse!
All around Catania are the so called "tavola calda" which literally means "warm table" and they serve all kinds of food/snacks. My personal favorite is the "arancino" , which is a pear-shaped, orange (hence the name, "little orange") ball of rice, minced meat, cheese and peas or you can get the vegetarian version with spinach. It is delicious and not much more expensive than a hamburger, of course you cannot compare the two when it comes to taste... It is typical from Catania.
Otherwise, you can get a pizza slice, which is usually good or a pizzetta (miniature pizza) or calzone (miniature calzone).
All these things are quite cheap, so for 4-5 Euros you can have a delicious snack/meal.
The only problem is that you will miss this when you go back home.