Vaping (E-cigarettes) can have similar effect on teeth as cigarette smoking!
E-cigarettes work by essentially heating up a liquid (typically nicotine) to turn it into a vapor that you can inhale. It adds "heat in the mouth" which changes the bacterial presence in the mouth. It dries the mouth out increasing the rate of tooth decay.
Vaping will also cause a darkening of the teeth. That's because, while e-cigarettes don't contain tar, they do contain nicotine. Nicotine will stain the teeth. Besides increasing your decay rate it can lead to bone loss and inflamed gum tissue.
Juul devices which look like a USB drive do not work by heating liquid, as most e-cigarettes do. It heats pods that contain nicotine and appealing flavorings such as mint, mango, etc which can contain chemicals that we don't yet know about. The device delivers high concentrations of nicotine quickly. A juul pod can contain as much nicotine as one pack of cigarettes.
Vaping is still relatively new. Time will tell what the effects of inhaling heated vapors have on the oral and systemic body systems.