I'd think it would probably take at least a couple of hours, depending on your metabolism. But if you only want to do it as sort of a test, I'd just start a day earlier. A day+ should be plenty of time for it's effects to kick in. How dramatic they will be, I don't know.
Yeah, usually about 2 hours after the pineapple is ingested. And as i've said: it takes two days for the fructose to metabolize out of the body, so your semen'll taste very sweet until then.
Asparagus makes ones piss smell to high heaven (bad). I can't imagine it not making cum taste foul. Different fruits should have a 'pleasing' affect on the fluid that carries sperm.