"Spill" is perfect. Yes, it is used commonly for liquid substance.
From Cambridge Dictionary
Spill: to (cause to) flow, move, fall, or spread over the edge or outside the limits of something:
I spilled coffee on my silk shirt.
You've spilled something down your tie.
Let's see if I can pour the juice into the glass without spilling it.
He dropped a bag of sugar and it spilled all over the floor.
Crowds of fans spilled onto the field at the end of the game.
It's clear from the second and last two examples that whatever that was spilled, was clearly not liquid.
"Drop" is a good option, too. Suppose she has a spoon full of solid food and she drops it?
From thefreedictionary:
To cause or allow (a substance) to run or fall out of a container.
You can also say:
Don't spoil your food.
or
Be careful, don't spoil your food.