Hospitality by Max Francis:

ONE CAN, TWO DIFFERENT DRINKS 

Hospitality in a can - You pour the complete contents of a can into a glass; the can is now empty. You then place a straw inside the can, and take a sip, just to make sure. In fact, the can is not empty, it now contains a completely different liquid! Pour this 'new' liquid into a glass to amaze spectators. 

BONUS EFFECT: 

Cocktail - You turn a cocktail shaker upside down to show that it is empty. Place the lid on the shaker and start to shake it as you would if you were mixing a cocktail. You then take the cap off and start pouring two glasses of cocktail. 

Use any can
Gimmick supplied
DVD with full explanations