The Empty Perk Bottle is a Power-Up featured in the zombies maps Origins and Zetsubou No Shima. In Origins, if the player has acquired the Golden Shovel and is in Zombie Blood, a dig spot will be glowing red somewhere on the map. These red dig spots will not change spots until they are dug up, and they are randomized each game. If these are dug up, an Empty Perk Bottle will appear which the player can pick up. When it is picked up, a new red dig spot will appear again randomly on the map at the start of the next round. Note that these dig spots are separate from the regular ones, and aren't located at the exact same locations, though they are typically found near each other.
For every Empty Perk Bottle dug up by the player, an extra perk slot will be given, up to 8. They may then buy an extra perk from the Der Wunderfizz machine or a Perk-a-Cola Machine. Going down and losing the perks does not remove the empty slots, as the player can simply rebuy all of their perks.
Using the Staff of Ice to spawn a Zombie Blood is a viable tactic to getting the Empty Perk Bottles quickly without having to depend on random power-up drops as much. It can be used to scout if the dig spot is near the Excavation Site or No Man's Land.
In Zetsubou No Shima, the Empty Perk Bottle can be obtained by completing the top most trial on the pillars in the Ruins of the Ancients or opening up a purple plant with yellow spots on it, though this is very rare.
There are sixteen glowing dig spots around the map. The locations are:
- Between Generators 1 and 2, just outside the laboratories.
- Between Generators 1 and 2, next to the Remington 870 MCS wallbuy.
- At Generator 2, at the cul-de-sac trench, in front of a wheelbarrow.
- At Generator 2, behind the Tank Station, right next to where the tank stops.
- Between Generators 1 and 3, halfway inside the Fire Tunnel.
- Between Generators 1 and 3, next to the B23R wallbuy.
- At Generator 3, next to the repairable barricade.
- Next to the Excavation Site on Generator 4 side, where one of the Staff of Fire parts lands.
- On the tank's path to Tank Station near one of the Staff of Lightning drop-off points (accessible from No Man's Land).
- At Generator 4, next to Juggernog.
- Next to the Excavation Site on Generator 5 side, on an Odin's footprint.
- On the tank's path to Church, near the dropdown to the cul-de-sac (accessible from No Man's Land).
- At Generator 5, in front of the soul chest.
- At Generator 6, next to the Remington 870 MCS wallbuy.
- Near Church, on the tank path to Tank Station, accessible from basement of Church.
- Near Church, on the tank's returning path, accessible from basement of Church.
- Collecting all Empty Perk Bottles, buying eight perks and obtaining the Double Tap Root Beer bottle from the Rituals of the Ancients box can be used to obtain nine perks, and can be only be done once in a game per player.