Thanks, I got the following from Milwaukee instruments support:
grasp the clear part of the soaker bottle firmly with one hand. Next, with the other hand, twist the black cap, lefty loosey, like a soda bottle cap. This will relieve the pressure that holds the cap in place. Once the pressure is loose, and the cap is also loose, grab the end of the probe, while still holding on to the clear part of the soaker bottle, and pull out of the probe from the soaker bottle.