In response to one portion of your message, feeling sluggish when eating after a period of fasting is usually the result of eating food that is more digestively complex and/or more plentiful than the body is ready to optimally process. In this digestively delicate stage, juice is the ideal - as it seems you have experienced for yourself - and as much as one might desire... and once the digestive system has emerged from its slumber during the juice phase then the next stage would ideally be blended fruit and/or leafy vegetables then the next would be unblended fruits and leafy vegetables and continuing to deepen little by little from here.
Eating more than we are ready at any stage will often result in sluggishness and by contrast, pacing ourselves optimally as we emerge from the fast should make us feel great every step of the way.