Gu works for me. I don't like really sweet things when I'm exercising so I stick with vanilla or orange which are not very sweet. I like the Gu Roctane too, which has limited flavors and I stick with orange-vanilla with that.

I used to buy Power Gels but that is much thicker than Gu, too thick for me.

Many years ago I tried Clif shots. They were too sweet for me, although I'm sure many people prefer them for that reason.