I did a couple of rounds of Prolon before I found out about water fasting. I think if you’re new to fasting it’s great to have the food packaged etc. It is super convenient and you save a ton of time and mental energy.
That said, now I know more I think it’s very expensive for what you get. The food isn’t great. It’s super salty. You might notice this more coming off a fast than you do going in to one. Personally I don’t see any benefit to what you’re proposing. You’ll be better off making and portioning your own soup and buying your own olives etc. The FMD sub has some DIY recipes.
What are you hoping to gain from this? If it’s to prolong your fast you may be better off having a small refeed and then going back to fasting.