I've used raspberry in a Berliner before, and just added a heap of frozen berries. Gave a nice colour, and a subtle flavour, but I reckon I needed double the amount to extract a bit more flavour (I haven't made it since).
Can't speak for pineapple, but I know of someone who tried it and had a real struggle balancing the acid from the juice once the sugars were fermented out.
Coconut is not something I've done before, but bear in mind it has a high oil content, which will ruin your head. You may be able to use coconut extract to get the flavour and not overburden the beer with oils. I think the milk/cream will both muddy your beer and add excessive oil (but this is purely based on theory, not actual practice on my part). Someone else may have real experience with the best way to add it to a beer.
A quick google has found the following links. Seems like most add coconut chips.
There are a number of ways to use coconut in your brewing. Learn to choose the right type of flavor, how to prepare it, and how to brew with it!
Dan from BrewConductor.com takes us through the best ways to use coconut in brewing.
Like most beers with an ingredient other than hops, malt, water or yeast, coconut beers stir up a lot of emotion in the beer enthusiast’s talking circles. Coconut may have more of a reason for this than most other flavor enhancers and that’s because the oils in coconut can quickly ruin any head...