If there’s a specific food they’re going after (and this can be something you’d never think cats would eat), don’t leave it unattended and uncovered on a counter. Cover it with foil, if you must leave it unattended, so you’ll hear it happening when the cat gets into it.
Get the cat down from the counter as quickly as possible whenever you notice them up there. A squirt bottle works. So does making a hissing noise at them (think Bilbo in Fellowship of the Ring); mother cats hiss at their kittens when the kittens do something wrong. Cats dislike sudden loud noises, so shaking a can with marbles or coins in it or clapping your hands hard might work, too.
What won’t work is punishing them after they get down from the counter, or if you find evidence that they were on the counter earlier. If you punish them after they got down, supposedly they’ll think they’re being punished for getting down, not for being on the counter in the first place. They supposedly don’t have the cognitive capacity to make the connection if you find evidence that they were on the counter and try to punish them for it later.
Make sure they’ve got high places where it’s OK for them to be and where they can keep an eye on what’s going on. A cat tree or tower is good for this. I got my cats to stop getting on the dining room table by putting a cat tower in the dining room. That satisfied their desire to be high up and keep an eye on what was happening there and in the kitchen without being on the table.
Make sure he has toys other than the bread bag that he can attack like he does the bread. If he has something acceptable to attack, the bread won’t seem so attractive. You may have to replace this toy every so often, when he shreds it. That’s life.
Some cats don’t like walking on foil. Mine don’t seem to mind so much.
Some cats don’t like walking on sticky tape. I found the sticky tape got in my way too much.
If anybody feeds them on the counter, that has to stop now. Never pet them or talk to them when they’re up there, either.
Make sure everybody in the house is on the same page about cats on the counter. A common problem is that one person thinks it’s OK for cats to be on the counter except when you’re preparing food, while another thinks that cats should not be on the counter at any time. You need to sit down and explicitly talk to your housemates or family members about this. Don’t assume they know that it’s not acceptable for cats to be on the counter- not everybody feels that way.
If one person is feeding and petting the cats when they get up on the counter, the behavior won’t go away, even if the rest of you punish the cats for it. Intermittent reward is what’s keeping all those slots players in Vegas there. It doesn’t discourage the behavior- quite the opposite.