Parenting advice...please comment

Ok, so I need to ask for some advice. JJ has been THROWING HIS CUP on the floor for months. We have been disciplining him with a very firm "no", smacking his hand (this doesn't seem to affect him too much, honestly). I just heard of the three strikes, which we've done, in a sense, I usually don't let him "have" the cup after 2 or 3 times, but he does still need to drink, especially now as he's getting over a cold. So, can you please help me, because whatever we are doing now, doesn't seem to be getting through! Julie and Sarah, I know you've read some good books, please comment. Thanks everyone!