humidity for a bearded dragon??

A mildly warm water soaking in the sink, tub, plastic bin, etc for 10-20mins a few times a week will do the trick to ensure they are nicely hydrated. Don't rely on the food giving them all the liquids they need to be properly hydrated!

Mine do regularly drink the fresh clean water when I soak them. But I do not put a dish in the tank.

Keep an eye on them as they soak. Just enough water to reach up to the shoulders. They often poo in the water. This is good and bad. Bad in that it messes up the water and you must change it right away. Good in that they will often learn to only poo during a good soak and this keeps their cage nice and clean.