What I do is use 1/3 alternative sugar (jaggery for me), 2/3 cane sugar in every brew. Earlier on I used more jaggery but found it caused a yeast dominant brew and slow fermentation. Jaggery is too high in minerals to use 100%, but I've found 1/3 jaggery works well and gives a nice caramel note. Apparently the culture adapts to different food over time, thats why you need to introduce certain ingredients gradually (like how some people wean the brew onto white tea). In my understanding, its best to use similar ingredients for each brew, so that the food is well matched to the bacteria in the starter liquid.