I think it depends on how much time you give yourself between eating and working out. If you want to eat something quick and then get right to working out, you should eat easily digestible carbs, like fruits or a piece of toast (white) with a little jam on it. Maybe half a bagel or something. I like to go with a banana and a piece of toast, quick to digest and not to heavy in the stomach. Maybe a little bit of (like 4-8oz) orange juice for an extra little boost.
If you’re giving yourself a little more time, like more than 30 minutes (or need energy for longer workouts) you might want to go for some more complex carbs. Wheat toast vs white, or oatmeal or cereal. Pair those with some fruit and I think you’d be good to go.
I’m not a nutritionist, but this is what works for me, hope this helps!