Hahahhahah, just go massage yourself to get full energy.
Dude, to tell you the truth its a bit more complicated than that. I had to grind 100k to impress the science girl.
And i wasted 72k only on energy potions, purchasing 99 to 99 potions and using them all to get to resistance lvl 31.
IT WASS DAMN HARD TO DO
And also a bit easier that going to the gym, then to the slums, have the massage scene, then go back to the gym