1/2 marathon coming up, snack ideas needed

All energy gels are not the same and while yes they are "sugar" different ones are based off different sugar sources so it is worth experimenting with a variety at home.

GU is Maldextrose which I have no problems with, except the fact that after sucking on them for a day they can cause some nasty farts.

Honey STinger uses homey in their gels.  

Inifit you can customize your blend.

Hammer Gels I can sometimes handle.  As others have said play around at home.

If it is the amount of carbs at a given time that you are afraid of then look at GU Chomps, Sports Beans or Shot Blocks.  Personally I can't chew and run so I avoid these.  You may also want to look a****ering down and energy gel and do that or a chew version with smaller amounts more frequently.

You may also find that as your body adapts to training and the requirements of the distance that your body will tolerate somethings better during the activity than it will when not engagaed in the activity.