Cola can be unpalatable to some patients and as it contains a fair amount of caffeine and sugar it can have other unwanted effects, particularly for diabetics.
This paper has examined the use of a vitamin C drink which contains no caffeine for improving uptake of itraconazole. This drink is shown to be very effective at enhancing uptake of itraconazole and the presence of its metabolite 7-hydroxyitraconazole (which also functions as an antifungal in addition to itraconazole, increasing its potency). It is shown to be very similar to cola, so this is a genuine alternative to cola and fruit juice for itraconazole users.
Is there is something about vitamin C that enhances uptake of itraconazole? This paper shows no such thing and states that this vitamin C drink had a similar pH (acidity) to cola. The acidity of the drink has always been stated to be what is important when choosing a drink to use to improve absorption of itraconazole - this drink is acidic so that is likely to be the reason why it helps rather than any specific activity of vitamin C.
The vitamin C drink also contains added fructose & fruit juices so will contain a fair quantity of sugar.
By all means consider drinks like this to help absorption of your itraconazole if you find it a pleasant alternative to cola, but think again if you need to avoid sugar!