turtle, I really sympathise with you on this one.
My DS is nearly 7 and up until christmas had never finished a full course of antibiotics. Mind you, he has AS and the typical superfussy bland diet, accompanied by super-senstive senses of taste and smell, which made it more difficult. Don't know why it works now, maybe he's just feeling more grown up now, or finally realised that after one lot of medicine actually did make him feel better that it might be worth the taste another time.
Anyway, what I've been advised in the past is to smuggle it in through his food, in something he likes. If this works it must be great, but does run the risk of backfiring. I've found in the past that putting it in a fairly strongly flavoured drink in a sealed cup or bottle helps (eliminates the element of smell ). At the moment we mix it in a medicine measuring cup with the same amount of orange juice, count down backwards (from anything up to 60!), and see how few swallows it takes, going for the world record. We also have full-sugar ribena ready for after, it's the only thing strong enough to take the taste away. And obviously brush teeth immediately after that! Not great for his general health, but better than weeks of being ill without taking anything.
Guess it's easier to reason when they're bigger, but they are also stronger. I've also tried reasoning, lying, threats, screaming, crying (me, inadvertently), bribery, holding his nose and pouring it in (just had it spat out into my eyes), syringe down the throat, putting it in fruit shoots as a special treat... You feel so awful, but also really don't want them to get more ill so it's hard to stay calm about it.
Guess that's probably not anything you haven't heard or tried already, but the not smelling it bit we had to work out for ourselves, and seemed to do the trick for a while