In English language, each is a word use to describe one of two or more distinct individuals considered separately but having a similar relation and often makes up an aggregate. Thus, each refers to everyone or everything that belongs to a group, regarded and identified separately.
In this context, the footballers are the group of people and each of them were given a cash prize for their victory in the championship.
Hence, the most appropriate word to fill the blank is "each" and the complete sentence would be written as;
"Each of the footballers was given a cash prize for winning the championship."
