If Hawke sided with the Mages, Sandal will be in the Templar Hall selling items and will also have the Storage Chest available.
If Hawke sided with the Templars, Sandal will still be there but
also in the Gallows Prison after the battle with Orsino. However his inventory remains the same but without any of the weapons or armor.
Note: Sandal's potion stock will restock after the confrontation with Orsino if they were previously bought out in the Templar scenario.