These are healthy ways of making competence between friends and colleagues. As the bets were simple and not big money was involved, these will not create any problem. Some might take it seriously, while the majority just take it as a game and just spend for their friend. When money is involved, people see it differently. When we consider it a meal or small money, they'll have the mentality that there's nothing wrong in spending it for a friend, and they won't take the bet seriously. These are part of fun and can be effective with a dedicated person, and not everyone will succeed with these kinds of self-improvement tasks.