My outside faucets have a plastic cap between the house and on/off handle that says anti-siphon, which are now gushing water when I turn on the faucet. When I turn this cap it spins in either direction and doesn't seem to do anything. 2 out of 3 faucets are doing this, one seems to be fine. How can I fix these?

My outside faucets have a plastic cap between the house and on/off handle that says anti-siphon, which are now gushing water when I turn on the faucet. When I turn this cap it spins in either direction and doesn't seem to do anything. 2 out of 3 faucets are doing this, one seems to be fine. how can I fix these?

If you can not remove the plastic cap to clean out the orifices then your only repair would be to replace them. In my book, (and I'm sure the plumbing inspector would disagree) you may replace them with regular hose bibs.
Good luck, Tom