"We are thirsty, but you are thirstier."
Translation:Vi er tørste, men dere er tørstere.
"Jeg tørster etter X."
It's used rather sparingly though, and usually in a metaphorical sense; having a thirst for knowledge and the like, rather than for something drinkable.
If you're simply yearning for a particular type of drink, then it's more common to say "Jeg har (så) lyst på X".