Water is basic husbandry
Most tarantulas should have access to a clean water dish whenever enclosure size allows. The dish gives the spider a dependable drinking source and reduces the need to guess whether it is getting enough water from prey or misting.
They do not drown easily in a normal dish
A shallow, appropriately sized open dish is safe for healthy tarantulas, including many slings. The common fear that a spider will simply drown in a bottle cap is misplaced.
Sling options
Very tiny slings can use micro dishes, small caps or carefully managed substrate moisture until a practical dish fits. Provide dependable access to water using a dish or, for extremely small slings, carefully managed moisture.
Keep it clean
Change dirty water and rinse the dish when it becomes fouled. If the spider repeatedly fills it with substrate, clear it and refill it without dismantling the enclosure.
Water dish versus misting
A water dish provides drinking access; misting changes surface moisture temporarily. They are not interchangeable concepts. Manage substrate moisture separately according to species needs.
Placement
Put the dish where you can refill it safely. For arboreals, a raised dish can be useful but is not essential if a floor dish remains accessible. Secure placement matters more than decoration.