Petstore employees often tell people that Bettas don't have any "special requirements." However, it's important to remember that they do have certain needs. Specifically, they require:
1) Adequate room to swim
There is a lot of debate as to how much room bettas require. Some people will tell you they require at least a 5 gallon tank. Others will tell you they can survive in a 1 gallon tank if at least 3 water changes are done per week.
However, looking at your video, it's pretty clear that the tank he's in is tiny. It's maybe 2 liters (0.5 gallons). That's not large enough to keep a betta in.
Also, the larger the tank, the easier it is to maintain good water quality, which leads us to the next item on the list.....
2) Clean, warm water
All fish require clean water. Without frequent water changes, toxins and wastes build up. If frequent water changes aren't done, these toxins will eventually poison and kill the fish. (You can lessen the number of water changes required by getting a larger tank, or by adding a filter and "cycling" the tank.) You can read more about water change requirements on OFL's water change recomendation sticky.
Also, Bettas are tropical fish. They thrive at temperatures between 76-84F. For most of us, that means adding a heater to maintain the proper water temp.
3) Good nutrition
Can humans survive on junk food? Yes... sort of. But we'd be better off eating some good nutrition. The same is true of our fish. Feeding them quality foods is better than feeding them junk food.
You didn't give the name of your pellet food. However, look at the list of ingredients. Bettas, in their natural habitat, eat insects (mainly mosquito larvae). They need a high protein diet. The ingredients in your pellet food should also be proteins. (Not grains or fillers.)