It is surprising to hear that squirrels are eating the plants. They will pick tomatoes, take one bite, and then throw them away, and do the same thing over again, day after day after day. You should probably avoid repellents as you will probably be looking to eat these tomatoes.

We would suggest installing hardware cloth over the vines/plants to protect them. Of course, this would mean that you would have to remove it to check for ripe tomatoes and to pick them. That does get to be a pain. Squirrels can be rather persistent, but eventually they will find something else to do with their time.

If it has been quite dry in your area, the squirrels might be attacking the fruit in search of moisture. If so, you could make water available to them.

Population reduction through trapping or shooting (provided either of them is legal in your area) is also an option. Details on these control methods can be found at the link below.

Online Resources
Internet Center for Wildlife Damage Management