The were essentially that, "Salt Pills". At the time they were given as a supplement when it was suspected that sodium levels would be dipping low due to heavy perspiration in the tropical environment. It was a common practice to provide them to workers in hot factories and athletes at the time.

Their use is much less nowadays because a massive amount of water needs to be taken in when you use them, most dieticians recommend an electrolyte heavy low sugar sports drink instead. Additionally most Western people have a very salt heavy diet already and don't need them.

Source: Cleveland Plain Dealer August 2012