Arby’s does offer such promotions regularly, so stay abreast with the latest offers.
For example, when you order Arby's Meal, you may get a shake or drink for $1. However, do check at the outlet you are visiting whether it’s valid during your visit.
Recently, they were offering a free milkshake, on buying a Diablo Dare sandwich costing $5.99. Do check whether this Limited Period Offer is still running.
On joining Arby's email list, you get free coupons from time to time. Do check the latest promotions.