Power a laser from Arduino using a audio cable/ jack plug

If you want both the left and right channels to provide audio you need to make a little mixer.

Two resistors (around 10KΩ) connected to the left and right inputs (pins 2 and 5), then joined together, will make a simple mixer. Then you link that to the LM386's IN + through a capacitor (around 10µF is usually OK).

Pin 1 links direct to the IN -

You ignore pins 3 and 4 - they are used to pass the audio through to another destination (internal speakers) when there is no plug in the socket.

^{simulate this circuit – Schematic created using CircuitLab}

This is a better circuit, because the BT module can draw quite a bit of current when transmitting and you would need a lot of base current to guarantee the voltage does not drop too much:

^{simulate this circuit – Schematic created using CircuitLab}

You could use a dual MOSFET such as the SiA519EDJ, which includes gate protection, for this application, or a single P-channel MOSFET M1 for the switch and a BJT or N-channel for the driving transistor M2. Another advantage of this circuit is that the current is quite low when the BT module is off- only 50uA.

To make it even more bulletproof against ESD on the jack, use a MOSFET with gate protection (as suggested) and put a resistor such as 2K in series with the switch.

Edit: Functionally, M2 turns off when SW1 is closed. That allows R1 to pull the gate of M1 up to +5, turning off M1. When SW1 opens, R2 pulls the gate of M2 up to 5V, turning it on, that pulls the gate of M1 down to 0V, turning M1 on and energizing the load.

You require two transistors in order to have the switch grounded and have the load 'off' when the switch is closed. If you could connect the switch to +5 then you could just have a resistor from the gate of M1 to ground and short gate of M1 to source (+5) to turn it off.

Use a breakout board to incorporate SMD packages. MOSFETs in through-hole packages don't tend to be very good at the low voltage/high current/logic level gate end of things.