Battery solution or distilled water? what to buy?

anyways the water in my car battery is low so i brought it to some tech guy and he said he wont fill it with distilled water as i requested him because he said it would shorten the battery's life he would only agree to fill it with battery solution. so i thought battery solution is only used if battery is very very new? i wanted to argue with him but im also having doubts what to use whether it's distilled or battery solution?