How can I get weak-tasting tomatoes? I love the weak tomatoes that you get at fast food restaurants like Subway. Whenever I buy tomatoes from the grocery store or the farmer's market, they're too strong and I end up throwing them out.

Do restaurants like Subway use weak breeds of tomatoes, or do they have some kind of process for making their tomatoes weak?
Buy "hot house" tomatoes, particularly off-season.  You'll be good to go.