This is it. The big time. I feel like it should be in all caps: EATING THE APPLE. Next to being that idiot juggling three flaming chainsaws, this is the number one way to impress your audience with your m4d 133t juggling skillz. Everyone will be impressed, and they will go away thinking you are some kind of juggling god among men. Unless they can juggle, in which case they'll know how easy this trick really is.
To eat the apple while juggling, juggle two balls and an apple in a three ball cascade, switch to two in one hand with the balls, and munch on that apple. Go on, try it.
See? I told you it was easy. It doesn't look that good yet - the good looks come from doing it smoothly and relatively nonchalantly and quickly. This comes from practice. With time, you won't even need to do any rounds of two in one hand.
So next time you see a juggler doing their thing, don't ask them "can you eat an apple and do it?". Of course they can. It just isn't very fun.
But it can be made more fun!
I highly recommend eaiting the apple gorilla style (or maybe guerilla - I've only heard it spoken not read it). That is, juggle three apples, and before your throw each one, make sure you have taken a bite out of it. This creates a big sloppy mess, and makes you look both silly and skilled. Very good for the applause-o-meter. As a messier alternative, do the exact same thing with three peeled oranges - the applause will be unstoppable, as long as the audience is sufficiently far away to not get splattered.
At one juggling festival, I saw the apple successfully eaten out of a 5 ball cascade (really 4 balls and one apple), and then I saw someone do it gorilla style (5 apples). It took a bunch of tries and seemed horrendously difficult, but that's about par for the course for 5 ball tricks.
The thing to realize about juggling is that the tricks that impress most people are not very hard. If you want to be entertaining, then learn to entertain once you have some basic skills. One good way of telling whether or not you have enough basic juggling skills is to try and eat the apple - if you can do that, and you want to be a busker, then it's time to learn how to work a crowd.