I personally use bottled water. The local tap water is treated with chloramine, and it tastes absolutely terrible, so I'm not giving it to my snake. Bottled water doesn't have chlorine or choramine, has minerals, and tastes a heck of a lot better, so it passes the "if it's good enough for me, it's good enough for my reptiles" test.

On the other hand, distilled water is not a good idea. No minerals.