At first I was totally convinced he doesn't but the hatchlings needed Energon too,right?And they were created after the Allspark was destroyed I guess so they didn't have a spark either.Who knows maybe there is a whole lot more to this than I can imagine.

 

And I don't think Galvatron has a spark either.

He's more or less an evolution of a cybertronian albeit with human interference.

 

Yeah and that's the point.He doesn't have a spark but probably needs Energon like the sparkless(?) hatchlings.

 

The KSI prototypes in all likelihood use a form of energon. When Prime's "ear" falls off in Cade's lab a green liquid oozes out. Also, when Prime punches Grimlock in the face in Grimlock's robot mode the green liquid squirts from Grimlock's face. Likewise, when the Dinobots and Prime are laying waste to Galvatron's KSI Decepticons some of the slain Decepticons gush with a green liquid. That liquid is most likely meant to be energon; it's just a different color from energon in the earlier movies.

 

All four three movies before TF:AoE have used various combinations of different color liquids for the internal biology of Transformers, including clear, black, red, green, and blue.

I'm reasonably certain that the blue stuff is Energon and everything else is akin to oil, lube, antifreeze, etc.

And I'm also pretty sure that the hatchlings were simply eating metal scraps like Brains in TF:DotM.

 

Starscream said in ROTF that without Energon the hatchlings will die.

 

There's a freakin' hole in him.

 

That is indeed what he said.

However, it in no way suggests that they hadn't ALREADY had enough Energon to carry them through to the stage of maturation and development at which we saw them. Nor did the scraps they were fed in the following film look anything like the glowing, energized depictions of Energon anywhere else in the franchise.

So like I said, I'm pretty sure we're meant to conclude that they were just feeding on metal scraps like Brains was in the same film.