Mine are very simple ones for emergencies
Kibble, ground up in a coffee grinder
Add water for thick soupy texture - but thin enough for a syringe if necessary to syringe feed.
Chicken w/rice baby food
a little Tone sometimes
My favorite for weight gain and ill fuzzies is:
Hills A/D prescription diet mixed with Dyne (found at revivalanimal.com)
Mix them together and add some Vitamins (Tonic) to it and liver drops if you need them for a female.
This one adds weight fast!