A spray bottle or mist pump is an essential piece of kit when keeping mantis. Cheap and easy to pick up from gardening shops, home ware shops like Asda or B&Q, or simply buy on online. Just make sure you give them a rinse first.
Most dry kept species don’t need to drink as they get their moisture from their food. Species like Idolomantis, Thistles (Blepharopsis mendica) and Violin (Gongylus Gongylodes) come from naturally hot arid environments with little rain or water to drink.
However species like orchids and Rhombodera that require higher humidity need the chance to drink. The glistening water droplets on mesh or plastic sides of their containers attract them to drink, they will sip up drops until they are satisfied.
Aside from drinking, the misting is important for raising humidity in the enclosure for moulting. If you think your mantis is about to moult then be sure to give the substrate or kitchen towel bottom a good spray. If the air is too dry for your moulting mantis they can become trapped in their exoskeleton and that never usually ends well. Even for dry kept species always mist enclosures so the substrate is damp if you think they are about to moult. This is especially important with species like Idolomantis and Spiny Flowers with lots of spiky bits that can get trapped in the exuvium (exoskeleton)