Is it permissible to give money to a poor family instead of buying a water cooler that was vowed?

A vow must be fulfilled if it is an act of obedience to Allah. It is not permissible to deviate from what was vowed unless there is a valid excuse, such as inability to fulfill it or the absence of a suitable place for it. In this case, it is permissible to deviate to the closest similar act or to give charity equivalent to the value of what was vowed. Paying money instead of slaughtering is not sufficient as long as fulfilling the vow itself is possible.