Patrick die now. Kudos to DeterminedX2 and TM for the awesomeness and Kool Aid.

Patrick may have been stupid, but he wasn't dumb. He knew hunger and thirst when he saw it. Or rather felt it. And as of now he was officially the most parched guy in the Pacific; in fact, he'd been feeling rather peckish since the whale gushed out all of that Kool Aid. (Silly Squidward's cheating at pinata, he remembered thinking at the time.)
He also knew that bringing up his thirst now would be inappropriate. Why it was so he wasn't sure, though Sponge now looked fit to cry his eyes out. Probably over missing his opportunity for Kool Aid.
But then, did he have much choice but to bring it up? nobody else seemed to want to offer him anything. They were all lying there, motionless; taking a nap, most likely. If he wanted a drink he'd have to go get it himself. Too much like hard work.

Offending SpongeBob seemed a risk worth taking right now. For he was that damn thirsty.

"Hey, uh, Squidward?" he hazarded, shooting his arm up like back in class.
Squidward, who had been celebrating the notion of killing said starfish at the time, wasn't too pleased by the interruption. "Do you mind? I'm trying to be evil here."
"Can you pass me a glass of that Kool Aid? I'm really thirsty."

Once Squidward had laughed for about five seconds, a pissed-off Pat gave it another try. "Why are you laughing at me? Is being thirsty funny? Is my suffering just one big joke to you?"
"No, no it isn't," the murderer finally managed to get out. "It's your unbelievably loose grasp on the world around you."
"Yeah, that too."

The smile dropped, laughter faded. "Wow, you're serious." A sad shake of the head. "Patrick, Patrick, Patrick. I am ashamed of you. Your life is in direct danger -- most of your friends have just died. Lifeless bodies choke up the air around you. And you're asking for a drink?"
"...Yeah."
"Are you actually TRYING to be that stupid?! Do you want to only make your death worse for yourself?"
"Well, OK," said the unknowing offender without thinking. "But I'd rather have a glass of Kool-Aid."

Squid seethed. This wasn't going right. He was supposed to be the one doing the torturing of brain here, not the other way around. "Ugh. Patrick always was going to be the hardest one to kill," he muttered, unsure of who he was talking to. "Too stupid for a regular death, too uncannily smart for a subtle death. What an oxymoron."
Patrick beamed at what he thought was a compliment. "Thanks. Takes practice."
Ignoring that. "The fool won't even realise he's dead when I do kill him. In fact... I don't know whether it would be more humane to let the fool live." Wild, virgin thoughts for Squidward the killer.

SpongeBob felt a prod in his side from far away. "Hey SpongeBob," he heard, "What do you think? Should I let Patbutt over there live, unknowing of what his fate would have been? Should he be the only surviving victim of my onslaught?"

Squidward was clever in this respect, far cleverer than most made him out to be. He knew that SpongeBob would be unable to answer, thus giving him a free path to do as he wanted.
He was right, too. SpongeBob was frozen. He wanted to speak, to say "No, don't hurt my best buddy", but he just couldn't - his throat was too dry, his whispers bitter. Bitter at the thought of having to say "yes, kill him".
He knew that he was totally powerless in the situation. No matter what he said, Pat would die anyway, even when let live. The eventual mourning feelings that would overwhelm his best friend when it was all over would likely prove too much.
His best friend. He was going to let his best friend die. Get murdered by what he now knew to be his beast of a ex-fri...neighbor. Murderers didn't even deserve to hold the title of 'friend' anymore, even in malice.

He had to let his best friend die now. It wasn't as if he had a choice.

"Well, SpongeBob? What do you say? Kill him, or spare him?"

The answer went unheard by his friend, but managed to surprise even the cold-hearted cephalopod.
"You've started your slaughter, Squidward. Now finish it."

"Ahem."
A cough from the other end of the room startled a newly-shocked Squid from his heaven-like stupor.
"I seem to remember asking for Kool Aid a few minutes ago," demanded Patrick. "Now fork it over."
Just like that, he seemed to get back into the swing of things. He had the opportunity - why waste it? "Of course, Patrick, I'm sorry. I'll go get you some right away." Grinning maniacally, Squid searched amongst his seemingly infinite pockets for his next weapon of choice; upon finding it, he ran over to Pat to give him what he was looking for.

"OK, Pat, this is a Kool-Aid making machine. Just peg these onto your hands, I'll flick the switch, and you can have enough Kool Aid to last you the rest of your life."
"Wait a minute. This doesn't look like--"
"You have no time to be picky, Patrick! Just plug them on!"
"Yay! I get Kool Aid!"
"Now just relax. It'll all be over soon."

The electrocution lasted for no time at all and yet for an eternity.

Shockingly (literally), Patrick didn't immediately die when 450 volts had passed. He just lay down, staring at himself. Look at all the Kool Aid running out of me. Hee hee...I'm a pinata.

"Hey SpongeBob, check it out, I'm a pinata.
"...SpongeBob? Can you hear me? SpongePal?
"Look at all this Kool Aid. Wonder how I'll be able to drink it all.
"... Whoa, I feel dizzy all of a sudden. SpongeBob, could you hold me?
"...SpongeBob?
"...I'm gonna take a nap now, SpongeBob. See you later."

Patrick never regained conciousness.

That was it. The last of the party guests had been snatched from mortality.

Now only two made up the population.

And this room suddenly wasn't big enough for the two of them.