I'm more interested in food business such as Snack, but I'm confused about what to make!?
I want to make a durable Snack, so that it can be mass-produced immediately,
Maybe in your country there is a snack that is currently in high demand?
How about this, you buy a box truck to convert or buy a used food truck. Start a food truck business those are very popular in the States and elsewhere. Construct a menu that compliments your chosen snack as you had mentioned. If you make good general food and people find you snack addictive then congrats you are on you way to completing your dream. Next buy another food truck or if you want to risk it open a restaurant. Continue to sell the snack and possible other condiments unique to your restaurant.
Really your idea for a snack is a good one but you have to get it out there. A restaurant or food truck is the best way to do it. Take Ken's Steakhouse salad dressings and marinades which started out in Massachusetts for example:
https://www.kensfoods.com/aboutOr California Pizza Kitchen that sells frozen pizzas that they also make at their restaurant albeit "fresher":
https://www.cpk.com/These two are examples where the auxiliary demand for their food product outstripped what the general restaurant environment could keep up with in terms of said demand which is a good thing to be a "victim of their own success" so to speak. This is the only victim you want to be and expand from then on.