Store bought suggestions:  Albertsons and some other companies have a nice line of tropical fruit juices, including mango-pineapple.  They're delicious,  cheap, and tasty on a hot day.

Pineapple Sundae Float
2 HUGE scoops of vanilla ice cream
1/2 small can of crushed pineapple
1 can 7 UP (or similar soda)
place ice cream in glass, pour about half the juice from the can on the ice cream PLUS half the crushed pineapple.  Fill to the top with 7 UP.  Enjoy!

Mango Fizz
   1 bottle of mango/pineapple juice
1 bottle carbonated water (you don't HAVE to use Perrier, but you can
Pour carbonated water into a glass until it is 1/3 full.  Finish filling with mango juice.  Add slice of pineapple, if you like.

With a little imagination, m'dears.