Washing fruit after cutting?
Short answer is - you can't avoid the little particles like the hairs from the flower bits when you cut a pineapple. Washing is the quickest way to get these residual pieces off the fruit - and yes, you do wash a little of the juice away, but this will be generally replaced by more juice in a short period of time, from where you cut the fruit (assuming the fruit is a juicy one and ripe).

Other options : a gentle scrape of the pieces off with a knife or other edged implement - but this requires you to closely observe the whole fruit and generally to pick them off a few at a time. You can also pat down with a paper towel, but this often doesn't work very well.