Most pills taste horrible when broken/ground up, even if you put it into something. I don't have a solution for pills unless you can get good-tasting chewable ones. Always ask your doctor or pharmacist if there is a liquid or capsule equivalent.. but be warned, you need to watch out for price differences between the two forms. If a pill is too big for the child to swallow, you could try cutting it in half, but you still need to get the child to swallow them. You could always try the Mary Poppins concept, and follow up the medicine with "a spoonful of sugar" or an equivalent 'bribe' or 'reward', something to make it fun or enjoyable if they won't take it simply because it will "make them feel better".
http://www.youtube.com/watch?v=i5IW9wK_HNg

If you open a capsule, you can mix it into applesauce and that's usually good as long as the contents arn't similar to a broken up pill. The contents of a capsule tend not to taste as bad as a ground up pill.

If it's a liquid medication, there are fairly good hollow-handle measuring medicine spoons that all you have to do is tilt back and zoom into the mouth/throat it goes. They're good for preventing spills, etc. as well as it helps to speedily get the medicine to the back of the throat and over the tongue, if its not the most tasteful stuff. http://www.google.com/products?hl=en&q=medicine+spoon

Try mixing it with food if it is allowed by the prescription

You can crush the pill or empty the powered contents into jam or pudding or something your child likes to diguise the taste. That works for most kids. As for liquid medicine, you can often ask for a specific flavor at your pharmacy, for example, cherry instead of banana if your kid like cherry flavor and doesn't like banana. Also, maybe give your child the little cup to drink out of as opposed to the syringe or dropper. My daughter will take her medicine much more willingly if she gets to drink it by herself in a cup then I praise her by saying 'you are such a big girl!'

You could try to teach him how to swallow pills, if they are not too large. I taught my daughter when she was 6 after I caught her hiding her chewable tylenol under the couch when she had a high fever. He might be too young, but it is certainly worth the effort to try.

I read about this method years ago in a parent magazine and it worked for both my kids. Get some chocolate sprinkles. Teach your child how to swallow the chocolate sprinkles. At his age you can make it a game and give him a treat for how ever many he swallows successfully. Don't make it too much of a game, or he might start swallowing everything.

The reason why this method works is that it teaches the mechanism of swallowing a pill, without the pain. If the chocolate sprinkle gets caught in his throat, it shouldn't bother him too much as it will melt away. This way you can show him how to have the pill/sprinkle on the back of his tongue and swallow it with a bit of water.

Good luck.