When you first begin playing Mann Vs. Machine, you might notice that many players have a Canteen, and you do not. If you want one on your first tour, you can craft one with 4 scrap metal. However, if you successfully complete a single game, you get one via drop, so crafting one then is rather pointless, and costs you precious metal.The Canteen is a powerful item that gives you temporary perks to aid your success. However, many people do not know how to apply these perks to their current class, or select a perk that does not aid them very well. This guide will go over the diferent types of Canteen and how they can be used for each class.

The Ubercharge Canteen acts like a 5-second Ubercharge from a regular Medigun. Your current class will become invincible for 5-seconds, allowing you to either attack at very close range, or get away quickly. Also, Engineers can get a shield set up around their sentry while this is in use. However, not many classes can make use of the Ubercharge Canteen.
The Ubercharge Canteen is best suited for Scout, Pyro, Heavy, and Medic.

The Critical Hit Canteen, sometimes called "Crits" gives you roughly 5 seconds of critical hits. All damage done during this time is tripled. Almost every class can benefit from Critical hits, but classes with high-damage weapons like Demomen and Heavies will find the most use. Also, Engineers' sentries will fire nearly twice as fast under it's influence.
The Crit Canteen is best suited for Scout, Pyro, Soldier, Demoman, Heavy and Engineer.

The Refill Clips and Ammo Canteen is a Canteen that somehow contains ammo for your weapons. It refills your clips and returns you to your maximum ammo limit. It is best left to characters with either a single clip of ammo (such as the flamethrower's canister of fuel), or high damage weapons that take too long to reload (A rocket launcher with an upgraded ammo limit). Also, Spy gets an extra sapper if he uses a Refill Clips and Ammo canteen, allowing Spies to stop more dangerous robots at a time. If you are not playing Heavy, Spy or Pyro, then this is best left to later rounds when you have upgraded your clip size.

The Refill Clips and Ammo Canteen is best used by Heavy, Spy and Pyro, and Soldier, Demoman and Scout on later rounds.

The Return to Spawn Canteen is a Canteen that acts as a teleport that sends you back to your spawn. This is most helpful when you are under serious attack and need to be sent away from the robots. It's biggest use is for Scouts, who can run through the robots, collect money for his team, and quickly head back to spawn to avoid death. Medic can also benefit from the Return to Spawn canteen, allowing him to return to spawn when under attack to preserve Ubercharge. When low on health, Medic can return to the spawn to avoid dying and losing his Ubercharge. When combined with Medic's ability to share canteens with his teammate he's healing, you can return to spawn with a severely injured teammate.
The Return to Spawn Canteen is best used by Scout and Medic.

The Upgrade Buildings Canteen is an Engineer-exclusive Canteen that automatically upgrades your buildings to level 3 outside of the setup phase. The best time to use this is between robot attacks during waves, when the next set of bots are running over the hill. It is also best used after all four buildings (sentry, dispenser, teleporter entrance and exit) have been placed, to ensure that your metal is reserved for sentry ammo.
The Upgrade Buildings Canteen can only be used by Engineer.

So now the last question that remains is, "So Which Canteen do I use for THIS class?" The answer is simple: Use whatever fits the situation. However, a handy guide has been placed below for each clas and their best Canteens.

Scout:

• Uber: If sneaking behind bots.
  
• Crits: If pulling most of the offensive.
  
• Ammo: If using a high-capacity scattergun.

Soldier:

• Uber: If up close to bots.
  
• Crits: If attacking from a distance.
  
• Ammo: If using a high-capacity rocket launcher.

Pyro:

• Uber: If up close to bots.
  
• Crits: If up close to bots.
  
• Ammo: If using a low-capacity flamethrower.

Heavy:

• Uber: If up close to bots.
  
• Crits: If not close to bots.
  
• Ammo: If using a low-caapacity minigun.

Demoman:

• Crits: During Setup and whenever laying many Stickybombs.
  
• Ammo: If using a high-capacity launcher.

Engineer:

• Uber: To protect Sentry.
  
• Crits: To increase firing speed.
  
• Upgrade: To quickly upgrade buildings.

Medic:

• Uber: If trying to get away easily.
  
• Crits: If able to share canteens with powerful classes (Pyro, Heavy, etc.)
  
• Teleport: If trying to get away easily.

Sniper:

• Crits: To do more damage faster.
  
• Ammo: If using a low-capacity rifle.

Spy:

• Uber: If up close to bots.
  
• Crits: If using the revolver.
  
• Ammo: For more Sappers, another Spy-Cicle, or to refill revolver ammo.
  
• Teleport: If you have been spotted.

So there you have it: A basic look at the Canteens and which classes benefit from them the most. I hope you enjoy Mann Vs. Machine Mode, and happy Canteening (It's now a word. Be quiet.)!