I'm all for fresh fruits and veggies, but not grapes! I used to feed my boys grapes with no issues, but I guess it can cause liver or kidney damage (can't remember which..it was one or the other though). I most often use oranges, apples, carrots, cucumbers, pears, peaches...just whatever I have on hand for myself
For training, I use little training treats that I get at petsmart. They're little meat flavored things that my boys love, and they worked very well. I actually ended up cutting them in 4ths so that I didn't fill their tummies up too much during training sessions.