And if I don't got enough in the tank, maybe I can just siphon enough
To fill up this last can, man will I survive in this climate or what?

from Eminem (Ft. Liz Rodrigues) – Survival Lyrics on Rap Genius

Meaning

Eminem is comparing his energy to car fuel. So he’s saying that he will siphon which means get more energy or fuel from another source. He is thus wanting more energy to survive this contemporary “climate” a.k.a. the rap game and stay relevant.
Again with the evolution theme he skillfully plays in this song.

Only got a gallon in the gas tank
But I’m almost at the finish line
So I can’t stop now

Eminem annexes a piece of wordplay to climate, he pronounces it so it sounds like climb it — effectively setting the allusion of conquering any obstacle in his field of vision.
The line can be seen as man will I survive in this? climb it or what? delivering the sense that there is only one option, which is to survive and overcome/climb it.

To fill up this last can(of whoop-ass)

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