How does what companies produce and sell factor in GDP?
This formula of GDP is an expenditure approach, which classify the country's output by category of final consumers. Therefore, you should determine who demands your product (ie who spends money to purchase your production): If $q_C$ is consumed by households, $q_I$ by firms, $q_G$ by the Government and $q_X$ is exported, then your new GDP is:

$$ GDP' = C \times p\cdot q_C + I\times p\cdot q_I + G\times p\cdot q_G + ( X\times p\cdot q_X - M) $$