Donuts is a donut shop that first appeared in a flashback in the episode, "We Messed Up." This flashback has been repeatedly shown in subsequent episodes, accompanied by saxophone music in a "noir" style relating to Gar and Carol.
Laserblast sneaks in there to disarm more of the weapons found, but was never seen leaving it. An explosion occurred inside it, and a few seconds later, it floated off the ground, shrunk, and then vanished. It's unknown whose lab it was, and what happened to it. It could have contained rare weapons or items like glorbs. It's possible that Laserblast met his death in the explosion.