title_body: Why do some cheap beers taste sweet?
upvoted_answer: The alcohol in beer is created as a byproduct of the yeast consuming the sugar in wort during the fermentation process.  For a beer to taste sweet, there are two possibilities:
  
  
  The yeast died before the fermentation process ran to completion.  There are various chemicals that can do this.
  The wort contained some non-fermentable sugars.  If the yeast can't feed on a particular type of sugar, then it is going to remain in the end product.  Lactose is a traditional example of such a sugar but some artificial sweeteners have a similar effect.
  
  
  Assuming that the flavour was intended, I would guess that this was (2): using non-fermentable sugars allows the brewer to know exactly how much will end up in the final beer.  It is also the only option if they do in-bottle carbonation, since that requires live yeast in the bottle.