a regular garden hose is just fine. People saying you "can't see" what's growing inside them...so, it's dark inside them, so it would be hard pressed to grow anything. However, a clear hose line IS susceptible to light, sun etc, and could create a "growing" environment, for that simple fact. Buy a new hose, cheap garden hose, whatever and use it. It'll be totally fine. Been doing this now for over 25 years and have had ZERO issues. Oh yeah, I'm a kid of the 80's and also drank out of the same type of hose all summer long.