Can of Slimoline is a slime based fuel comparable to gasoline. It was added in 1.4.0 as part of The Useful Update. This item does not exist in real life, but was added rather as a fun item for the mod that does serve some utility. In game, there isn't very much you can do with slime. Eventually slime blocks, sticky pistons, and leads get old, but you may still have some slime balls left over yet! This item allows you to craft them with some other things to make a usable furnace fuel. This fuel has a very high burn time compared to its ingredients which only burn for short amounts of time, so it makes slime quite profitable.
You can get a Can of Slimoline by crafting a Slime Ball, Gunpowder, and Coal Dust in a shapeless crafting recipe as shown below.