Brocho before eating this: Say the bracha that applies to the ingredients which make up a majority of the cocktail. If one is not sure which bracha is the majority, say Borei Pri Ha'adama.
Commercially produced fruit cocktails are usually Borei Pri Ha'eitz (because the Pineapple is only a minority)
Brocho after eating the proper shiur of this: Borei Nefashos
Source: The Laws of B'rachos (page 368)