There are no small craft breweries that I know of adding corn syrup to their ales. Some use Belgian Candy sugar or beet sugar to up the ABV in strong ales and double IPA's becuase it is cheaper than Pilsner Malt (the most common malt in IPA). The big commercial breweries do indeed use rice and corn and other sugars as fermentable adjuncts. There are several possibilities of why some beers make you feel bad.
I'm tired now and this is a long discussion that I will get back to tomorrow. I actually need to be up early to dump grain in the mill for brew day.