For me, feeling healthy and clean after a cleanse is enough to keep me eating pretty clean (for awhile, at least
) After all, why go to all that trouble just to go back to eating a bunch of junk?
Truthfully, you'll probably gain a little bit of the weight back - the part you lose first is water weight, and when your body returns to normal, it'll probably go back to storing some of the water lost during the cleanse. You absolutely can keep the fat off, as long as you keep your diet and exercise levels in check.
And yeah, cutting out the energy drinks is probably a good idea. Hopefully you'll gain a lot more natural energy through the cleanse