From the Super Mario Wiki
The Ignition Barrel is a type of barrel in Donkey Kong Country 3: Dixie Kong's Double Trouble! Only a single Fuel Barrel appears in the game, during the final level Rocket Rush. Near the end of the level, Dixie Kong and Kiddy Kong have to make their way to the bottom of the cliff-side in a Rocket Barrel to find this lone Ignition Barrel. When the Kongs reach the bottom of the level, the Rocket Barrel hits the Ignition Barrel, breaking it and causing it to ignite the Rocket Barrel up to end of the level.