Ordinarily , unless you have VERY LOW relative humidity coupled with heat wave conditions, your dragon should be getting sufficient moisture from it's food (live insect, fresh leafy greens and grated or chopped veg , fruit and berries).
Are your dragon's poos and urates soft and moist.... he's well
hydrated.
If they are dry and hard , he needs some extra
hydration.
You can places droplets of water on his snout for him to drink, if he's
thirsty he'll lick them off, or give live insects (always attractive to a dragon) ie silkworms , hornworms , even well
hydrated crickets , locusts or roaches will do.