Inside a closed bottle of a fizzy drink an equilibrium is established involving carbon dioxide.

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To make the drink fizzy, carbon dioxide is pumped into the drink at a pressure above atmospheric pressure. The gas dissolves:

CO₂(g) _↓  CO₂(aq)

A cap is screwed onto the bottle so that the gas can't escape. A gap is left (the headspace) between the drink and the bottle top. A dynamic equilibrium is established between the carbon dioxide in the drink and carbon dioxide in the headspace, with carbon dioxide moving between drink and headspace and between headspace and drink.

CO₂(aq) _∏ CO₂(g)

The reaction is at equilibrium as long as the temperature doesn't change.