A consumable energy drink for the Scout, that after it has been drunk, will give the Scout a sugar rush, allowing him to dodge bullets for a short period of time. The down-side to the Bonk! Energy Drink, is that during your sugar rush, you cannot use any of your weapons. After use there is a cooldown before it can be used again. Bonk! fills your secondary inventory slot, so you have to trade out your pistol or Crit-A-Cola.
Added to the game during the "Scout Update", it originally gave the Scout invulnerability for 6 seconds. Though the user wouldn't take damage while under the effects, push-back from sentry guns and compression blasts still applied. Also, if the Scout was lit on fire while under the effects and the after burn continued after the drink wore off, the fire damage would ensue. The downside, previously, was that once the energy drink wore off the Scout was have a 56% speed reduction, which was needed for the achievement Retire the Runner. This speed penalty was removed and replaced with a cooldown bar on April 28th 2010. The receive the Retire the Runner achievement now, the scout must be killed after the effects of Crit-A-Cola wears off.