How to minimize waterback flow mess when cutting an in-service pipe
I use dry ice on metal plumbing when the service valve is not functional or not in the area. Grocery stores have had dry ice in several states I have lived some times you have to ask and it is sold by the pound.
I use a hammer and screwdriver to break some chunks off and a cloth to hold the dry ice in place. I pack around the pipe for 1-2” and hold it in place for a few minutes then cut the pipe. Or in your case remove the shark bite.
The dry ice may last up to an hour depending on how tight you pack it around the pipe and how thick. I have used this method for years with great results much cheaper and faster than a commercial unit to freeze the pipe.
Caution instant frostbite if you touch the dry ice. I use heavy welding gloves but any well insulated gloves will probably work.
The “smoke” coming off dry ice is just carbon dioxide (the fizz in soda is carbon dioxide) it’s non toxic but fresh air is needed, just keep the door open if it’s in a small closet.
Last the left over dry ice can be fun at home wrap in newspapers to help it last longer and put in a cooler, you can put it in water and it makes a neat smoke again non toxic, I have used chunks like ice cubes in punch bowls for a special brew of Hawaiian Punch the kids love because of the smoke.
I am sure there are other instructions using dry ice on line with photos but I have done this for almost 50 years and never broken a metal pipe it works best on copper.