To create a variety of sizzling and crackling sfx take some Alka Seltzer tablets and place them on top of a piece of dry ice. Pour various liquids like water or any carbonated beverage over the tablets and ice. Mic needs to be close.
Experiment with poking this concoction with a metal implement like a very large nail or small crow bar to get some nice little sizzly impacts. Wear eye protection.
– Seph Lawrence