As you're asking about teen boys I will happily push my DD (16) shpping habits to the back of my mind ( She loves her brands )
DS : 19yo, University student , 5'10" , very thin ( I think his waist is 26"-27" . Near impossible to buy the leg:waist he needs so they normally hang round his arse in the way that makes you want to give him a wedgie
)
I usually pick up clothes for him , sometimes DD will suggest something , though usually she'll say he only needs a Primark top because he doesn't care , while she wants a Champion or Adidas one !
H&M jeans (he doesn't care about brand , more fit and colour)
Nike trainers (I dragged him into Sports Direct and asked one of the sales staff )
He has a The North Face fleece
Trespass waterproof ( minimal logo and function over flashy)
H&M T-shirts (sooo soft)
H&M hoodies
Primark
Underwear -H&M, some Levis , various ones picked up in TKMaxx (again the fit for his tiny frame rather than brand)
He has a couple of jackets from Costco, no branding but really nice , well fitting and warm
Fleece from Berghaus (sp)
All loungewear/nightwear Primark or Sainsbury.
Christmas present dressing gown from Peacocks .
I am really lucky he's not into brands as DH and I still buy everything for him. 