Two things. First, you need to be properly hydrated. One bottle per hour minimum.

Second is nutrients. The form is not important, it's the quantity of things like calories and sodium that matter. The format is up to your personal preference.

I can't tolerate solid food on most bike rides, so I stick with Gatorade and Gu (regular and Roctane). Other people prefer to have regular food with or instead of gels and chews.

You do want to ingest things that are easy to digest, so limit the protein and fat content if you go with regular food. One benefit of electrolyte drinks, gels etc. is that they are formulated so that your body gets the nutrients into your system quickly.

You should experiment with different things while you train, and don't try anything new the day of the big event.

Good luck!