Everyone reacts differently, but DH canNOT drink a typical HFCS soda without freaking out then passing out (jacks up his blood sugar then he crashes), but he can drink butterbeer without even getting into a funny mood. (his mood is almost better than his meter for letting us know what his blood sugar is)
But everyone is different. All I know is that when I got that sneak peak at the ingredients, it was NOT HFCS which makes all the difference for DH.