Energon comes from whatever the writers want it to.
You can convert electricity to it, light to it, turn organics into paste to make it, convert metal into it. It can sometimes only be refined from raw crystals, which are sometimes so toxic they need a layer of organic material to even be on the same planet as them.
Sometimes it is liquid, sometimes solid sometimes pink, purple, blue, rainbow sparkles in glowing white suspension, black, green, or yellow. Sometimes explosive, others currency, others nonsolid energy.
Sometimes it is food, sometimes blood, sometimes air. Their guns need ammo clips, or it leeches directly from their body. Sometimes you can recycle it with proper conservation.
Sometimes it is the blood of gods. Others, a random naturally-occurring element.
Earth is apparently covered in it and nobody noticed.
The only consistent thing is they need more.
Diamond sweat could maybe be Energon.