I have a couple of mods to keep my S days under control.
No Eating from Packages (NEP). Anything you want to eat has to go on an individual plate or bowl (eating off serving plates is not OK) before you can eat it. Food packages must be closed up and put away before you can start eating. This means you can't do stuff like keep a cereal box on the table while eating breakfast- the box has to be closed up and put away in the kitchen. This makes it harder to get more, which is the whole point. There may also be some benefit from having to see everything you're going to eat, all laid out together. If you eat too much, it
looks like too much.
Sitting. This one's even simpler. No eating in any position other than sitting.
I also have a rule that packages of food may not be stored anywhere other than the kitchen, pantry, or (in special cases) basement. That means no stashes of food in my office or bedroom, no candy dishes in the living room, and so on. If I want food, I have to get up and go to the kitchen to get it.
Another rule is, no hanging out in the kitchen. You can prepare meals and clean up after meals there, or do general housecleaning, but it's not a place to hang out and read, talk, or watch TV. There are other places for doing those things (that's what a living room or den is for, and the chairs are probably more comfortable to boot). Per the above rules, there is no food in those places, unless I brought a plate or bowl of food there.
When you buy sweets or snack foods, the goal is
not to get the most food for the least amount of money. You don't need a lot of sweets or snack foods. Buy smaller packages. Yes, it will cost more per pound (or whatever unit the food is measured in), but people tend to eat more from larger packages. You can do more damage by pigging out and eating all of a large bag of snack food than you can with a small one. It's better to limit the possible damage if you go off the rails.
If one of your problems is overeating at meals, you might want to try serving food buffet-style instead of family-style. That means the food is not put in serving platters that go on the table. Instead, any serving platters stay out in the kitchen (or you can serve directly from pots), so you have to get up if you want more of anything.
Another thing to try is making less food overall. People tend to eat more if there is a lot of something available. That whole idea of "make extra so you can have leftovers later" doesn't work for all of us. Unfortunately for me, Nicest Husband is totally wedded to that idea
He doesn't like it if there isn't enough for leftovers from a dinner.