It’s not possible to interrupt the 3V3 line on the Electron. One solution to this is to power your sensors using a MOSFET controlled by a GPIO line so you can power them down. This is more common to preserve battery power, but also can be helpful for resetting devices.
It’s actually possible on the Boron by using an external circuit to control the EN line. There’s an example of powering down the Boron for 30 seconds remotely here: Deep Reset Tutorial .