nothing, not anything

I don't buy anything.

私は何も買いません

I don't buy anything on impulse.

私は何も衝動的に買いません

I don't buy anything on impulse online.

私はオンラインでは何も衝動的に買いません

I don't buy anything on impulse online even during a sale.

私は割引期間中でもオンラインでは何も衝動的に買いません

I don't buy anything on impulse online even during a sale unless I need it.

私は必要でなければ割引期間中でもオンラインでは何も衝動的に買いません