I doubt seriously that you experienced a die-off symptom considering you’ve been on the diet for two days, especially if you had diary on the first day. Are you doing anything else yet, such as an antifungal?
It’s fairly normal for a person on the Candida diet to go into ketosis, and it doesn’t hamper the treatment.
There’s no reason why you should become dehydrated on the Candida diet, not if you drink water the way you should. Part of the treatment is to drink plenty of water at mealtimes as well as between your meals. Not only will it keep you hydrated, but it will wash out the toxins as the Candida die off.