I tried this last year. It did not deter the little rat-bastards. Neither did a fake owl I bought at Agway.

Some ideas I have heard of, but not tried:

Hang red Christmas balls from the plants. They look like tomatoes, but the squirrels get the idea that the tomatoes in this plant are not edible.

Tin pie plates suspended and blowing in the wind so that they clash into each other.

A dog.

This year I am growing in a new location in a different neighborhood. I have a freakin' groundhog on the prowl. I placed small spinning wind toys around the garden and didn't see garden damage as long as there was wind. Then I put an 18-gallon tupperware container upside-down over his hole. I haven't seen him since I did this 8 days ago.

Maybe the spinning wind toys would work for squirrels? I don't know. They are $1 at our local Dollar Tree store.
Fred in Maine