Hello...
In Ayurveda while planning any medicine or diet, agnibala or digestive power is given importance, also some food items are considered as can be taken on all days and some others are told not to be taken on every day.
I think the concept you told "three months take and leave one month" is due to this fact
You can take both dry smoothie and also antioxidant juices, if your digestive power allows you
You can take these in an alternative manner so that you are not taking these on a daily basis
Also while taking please consider if you have any allergy to any of the ingredients, if anything noticed pls stop.
In case of preservatives, you may put these fruits in turmeric water for half an hour then wash and use
Next Steps
for more details you may consult through practo