Samnaun is a duty free area in Switzerland and the more popular, main route up is from the B180 Reschenstraße in Austria.
There is a pleasant winding mountain road from Vinadi on the 27 in Switzerland that winds its way up and joins the main route near the Swiss Border Crossing. This is not a fast road. It is narrow, with very few straights and some interesting old tunnels carved through the living rock. Most of them have tight bends inside, are very dark and motorcycle headlights tend to do little to illuminate your way. Several are also single track and you have to look across the mountain side to see if traffic is entering from the other end. First come, first served but it doesn´t always work out that way. The last time I was there, October 2015, there were some major road repairs taking place and on the whole the road is looked after. This is a classic small mountain road and fun to ride.
Just before it joins the major route there is a Petrol Station where cheap fuel is available and also a Duty Free Shop and Cafe. Travel on up to Samnaun itself and you will find a typical Swiss Ski Resort with several petrol stations offering cheap fuel and many shops claiming to be duty free. You decide if they are cheap but be mindful that Switzerland is not in the EU and Duty Free Allowances apply when crossing back in to Austria. You can be checked at the border or subject to a mobile customs check travelling down the main route. 200 cigarettes over the limit attracted a €200,- fine or €100,- if you surrender the excess a couple of years back. Guess which idiot forgot the EU Status.