I know of no evidence that coffee grounds will deter squirrels. With what species of squirrel are you having a conflict, and what is the setting and damage involved in the conflict?

Thank you for your reply, Dr Sanchez. 

Vinegar is an acid and will kill the plant material it touches, so don't spray that on plants you want to keep! I would ask your master gardener about whether coffee grounds add any value to plants - I imagine if you added them to compost, then they would add some nutrients, but make sure you consult with a master gardener on questions like that. You could submit a separate question in AskExtension. 
To keep squirrels from digging in your pots, either buy some "hardware cloth" (welded wire), chicken wire, or similar metal fencing mesh, make a cap to fit the top of the pot, and then secure it so the squirrels can't just flip it off. Alternatively, I have noticed that some people rescue and repurpose used bird cages to create pretty plant protection enclosures!