Johnny Wee‘s image of a Alexandrine Parakeet (Psittacula eupatria) eating an unripe rambutan fruit (Nephelium lappaceum) suggests that it prefers the seed rather than the flesh. The image was taken at Seletar in Singapore. It must have been an escapee (see comments).
An earlier post on a Rainbow Lorikeet (Trichoglossus haematodus) LINK failed to show whether it prefers the flesh or the seed. In the case of the Blue-crowned Hanging Parrot (Loriculus galgulus) LINK it is obvious that it is eating the flesh.