I'm wondering are e-cigs still bad for you if they contain no tobacco/nicotine?

Nobody really knows: Even the ones that basically result in water vapor are using propellants like propylene glycol, and many of them have flavorings, colorings and additives like preservatives. At this time, there is no requirement for the manufacturers to even tell you the exact ingredients, and no long-term studies are available of the effects of inhaling all these things over time.