well, you could do the humane thing, put him out of his misery, instead of just letting him waste/fade away slowly, and possibly painfully...

or you can hold on to slight hope he might pull through...

give him some grass maybe, like force it down his throat (i dunno how you're going to accomplish that tho) when a dog or cat is sick they eat grass... could help....

assuming you know he's about to die, i'd just put him out quickly... i'd do it with any pet i loved too... watching them suffer is worse then them dying period...

it's not exactly tasteful, but you could shoot him in the head if you had a pretty powerful pellet gun or maybe a .22, stick him in a ziplock bag and suck out all the oxygen or smash his head with somethin heavy...

o.0 i'm afraid you may take this post the wrong way, i just know i wouldn't wanna watch a pet of mine suffer... and you don't exactly take a rat to the vet to have it put to sleep.