By not trying anything new I was mostly referring to don't eat/drink something that you haven't eaten before. Since you are doing the aquabike and not running that gives you more flexibility as most people can typically handle solid foods better on the bike.

I am actually doing a HIM distance in 3 weeks, my coach recommended that I take in 150-200 calories per hour on the bike but this is mostly to fuel for the run.

My pre-race breakfast is always PB on a whole wheat bagel and a banana.
For all distances I usually have a gel 20 minutes before the swim, for sprints I don't eat anything else and it just electrolyte water on the bike. On the Olympic Distance I added some power bites on the bike as well as a bottle of GU Brew (I can't stand most drinks) and some power gels on the run.

My plan for the HIM is to have 2 bottles on the bike (140 cal each) and a small Clif Bar in the first hour on the bike. The run I will use a GUs, I find for longer runs about one gel every 45-60 minutes.

I find I need to mix it up as if I just to gels it upsets my stomach. The key thing is to find what works for you.