Can I ask, what actually is it? what's the main alcohol constituent - some sort of cheap wine?
How strong?
(always an important consideration for me - otherwise it's my normal water with limes tipple)
It's a cheap full bodied red wine; traditionally it is simmered with orange zest, spices of your choice and some sugar. I was first introduced to gluehwein when I was working in Austria and I had never tasted ANYTHING so delicious in my life. The Christkindl brand which Lidl stocks is the nearest I can get to the flavour I remember from over 50 years ago; when I came across it by chance in Berlin over 20 years ago I was ecstatic to find it was a ready-made product, and to find it in Lidl when I returned to the UK from Australia was like finding heaven in a bottle!
All of the UK brands and supermarket brands of ready-made mulled wine are too ... something ... for me. All different things. One has too much ginger, another is overpoweringly cloves, another is too tannin-y; only the Christkindl brand is tastes 'right' for me - what I do is add some water and some orange juice and (sometimes!) put a small tot of brandy into it when it's heated. THEN it is perfect.
It's one of those things that can be as alcoholic, or not, as you prefer. If you heat it slowly to evaporate off the alcohol, and dilute it somewhat with water/juice, obvs it won't be as alcoholic as if you nuke it and put a dash of brandy in it ... I've put the bottles at the back of the cupboard until the end of the month so can't easily get at them to see the bottle's alcohol w/v or %. It seems stronger than it is, because of being heated I think it's probably absorbed faster!
Whittards uses to make a mulled wine flavour instant tea which, while it obviously didn't have the alcohol content or effect, was nevertheless a pretty good replica of the general flavour profile of what I think of as good gluehwein; its main (and quite serious, IMO) fault was that it was too sweet. It was a very pleasant diluent, though, for some of the over-spiced and even slightly bitter British mulled wine brands.
Sadly I can't make my own as it is something that's better brewed 'in quantity' for serving to a group of people and making an individual mug of it isn't really a practical proposition, hence my delight at finding a good ready-made one.