Fake, non-drying blood?
By - icarus_rises1
Corn syrup with blue and red pigment. It will eventually dry, but it takes a while.
It will only dry if it is exposed to the air. If it's placed in a non-permeable container, it shouldn't dry out because there's nowhere for the water content to go.
That said, it's cheap and it should be good for 3-4 days at least so you can just make new any time you need it.
Maybe just paint the inside of the jar deep red as if it is filled? Or like put paint in it but pour most of it out and let it dry inside the jar. But anyways the corn syrup would last a while if you don’t open it