I go with powerbars and coffee.
I love my coffee in the morning, but whenever I drink coffee and a glass of water it seems I have to pee about every 45 minutes to an hour. I will usually take a gel with caffeine in it about 30 minutes before training or racing so I can still get my caffeine without having to pee as much.
You need to practice this in training. One of your long training days, get up and eat what you will eat on race day. For me, it’s a normal breakfast. A bowl of cereal with banana in it, and I’ll add a bagel w/peanut butter. I like to finish eating at least two hours before the race.
I know this might sound crazy but prepare a breakfast the night before and hydrate the best you can. Set your alarm for a couple of hours before you are due to wake and have your breakfast then (no coffee or fruit juice). then go back to sleep and when you wake start hydrating. So long as you have got your body clock used to early nights and early mornings you will be fine. Maybe a have a snack before the race but something light. This will ensure your carbo loaded for the swim. this is important as your body won’t be able to process a normal breakfast in time for it to benefit the swim. As soon as you get your change bag for the bike have some food in their good to go. Eat well at the start of the bike after you have settled.
This is what I do but everyones different, this may be difficult if you are mega nervous as you won’t get back to sleep.
Like many others here, I go for the bagel with PB. Sometimes I have oatmeal with a banna, but most of the time I hate having a lot of food in my stomach before races so I tend not to eat a whole lot before the race and I take in lots of gels/snacks during the race. The coffee, for me, is a must no matter what.