Because this is one I don't do any more, I'm only including it in the comments

Bread rolls are great, but they leak out the sides if you just cut them horizontally. As a teen, I used to excavate from the top, making a small external hole just big enough to fit my fingers in, and a large internal one by a mix of squishing the insides and tearing bits out and eating them. Then, fill with a mix of jam and cheese (or other things, but this was much usual one), stick in microwave for a minute, and then head out the door with a nice hot snack.