Are these the same variety you grew last year? What is/are the name/names of the variety/varieties? Where did you get the seed (or were they plants)?

Are the tomatoes spotted in any way? Unevenly ripened? Is the vine diseased or struggling?

I don't remember the variety. They were plants. They have nothing unusual as far as disease - some early blight. They are planted in the ground. I put in 3" of compost this year and fertilized with fish emulsion a few times. When planted I used tomato tone. I can't understand the bitter taste.
I don't know if bitter tomatoes are a result of fertilizer problems or watering and weather conditions.

Variety really needs to be known to get much more of an answer. Purchased at home depot? Lowes? Nursery? Free from some where? Who saved the seed or purchased the seed for the grow out?

Are you familiar with stink-bug damage? I'm not sure if they taste bitter; I try to avoid them.
http://www.ipm.ucdavis.edu/PMG/E/I-HM-ECON-CD.004.html

Otherwise, in the absence of disease, it's probably variety.

If, for example, the second year's plants were grown from seeds someone had saved from a hybrid, the result would probably be something very different from the hybrid, and that might be something horrible-tasting.

Or the seeds might have been from an accidental cross.

Some varieties have strong flavors that many people don't like.

Sorry I just don't know the variety. They were plants I purchased early spring. I lost the tags. But I'll look for stink bugs. I purchased them at a local college plant sale. They grow the plants in their greenhouse and have a sale every spring. Who knows where they might have gotten the seed. I'm thinking of pulling them out because they don't seem to get any better over time. Sometimes I bite into one and it is so bad I spit it out. Never tasted a tomato so bad before.

Any suggestions on cherry tomato varieties that are sweet?

Thanks.