Mix 4 teaspoons icing sugar with1 teaspoon baking soda.
Make a pile of sand on a heat-proof surface, and make a dent in the middle of it.
Pour fuel into the dent, then add some sugar/baking soda mixture.
Long black "snakes" of carbon are extruded, made up of carbon and carbonate, puffed up with carbon dioxide gas. They crumble when they are touched (and make your hands black).
The reaction smells like marshmallows over a fire.
C12H22O11 (sucrose sugar) + 12O2 → 12CO2 + 11H2O (g). This is complete combustion of the sugar in oxygen, which produces heat which makes the reaction continue. The water vapour escapes.
There are also some reaction products that are not made with oxygen (which happen in the centre of the pile):
C12H22O11 (sucrose sugar) → 12 C (black of the snake) + 11 H2O (gas).
2 NaHCO3 (baking soda) → Na2CO3 (carbonate that is also part of the snake) + H2O (gas) + CO2 (gas, which puffs up the snake)