Unfortunately, it doesn't really work. There may be a slight change, but nothing incredible. Your best bet is to go to an adult store and buy a flavored lube for a change in taste.
Eating or drinking stuff to make it taste better doesn't seem to do much- but being careful on not eating 'smelly' stuff may make it a bit nicer.
Different people claim different results with this. Those claiming the best results do more than drink pineapple juice.
The following combination of things seem to help the best, from what I've heard.
Drinking any sweet fruit juice will help, pineapple is the best though.
Don't smoke.
Don't drink coffee.
Don't eat/drink bitter things.
Don't eat red meat.
Don't eat asparagus.
Keep salt intake to a bare minimum
That said, there's no guarantee. Results are supposed to be evident after a few days with it really kicking in after a week or more. One source claims you need to expend your semen three or four times before the change becomes evident.
Worth the effort? I don't know. I'm not giving up coffee, red meat or asparagus. I like my cigars and scotch or wine, so don't even go there.
If she can't handle the taste now, changing it by doing these things isn't going to help IMO.
I did a test for this and drank pineapple juice for a whole day - and didn't eat any greasy foods. My girlfriend said she noticed a signifigant change...depends on the person maybe?