You don't have to use water as the liquid in your bread. Enriched breads use milk and/or eggs. We have recently had questions about breads which use orange juice.
On the technical side, you have to adjust recipe a little. Pickle juice doesn't have much dissolved solids, so no need to adjust for that. However, it is very salty, so you should reduce or completely leave out the salt. The acidity will help with gluten development and also with breaking down the starches in flour to make them available for chemical reactions which produce more flavour, so this is a good thing to have. However, yeast itself has some strong pH preferences. It grows best in a slightly acidic environment, but if the dough gets too basic or too sour, it will slow down or not grow at all. I think that the diluted vinegar in the pickle water won't oversour the dough, but it would be a good idea to make the poolish with pure water and only add pickle water for the dough itself.
As for taste, I can't say that much without ever having tried it, but my intuition says that you will get a whiff of pickles, but not a full-blown taste. After all, bread made with orange juice doesn't taste like biting into an orange. I think you will notice the difference, but you will still have to add pickles to your sandwiches for taste (and they are needed for the crunch anyway). As for horrible, it depends entirely on personal taste. I am not a fan of pickles or soured breads, and wouldn't eat it. There are people who drink the pickle water from the jar; I think they will enjoy the pickle-smelling bread too. If you are a pickle fan, I think it is worth a try, if it doesn't work, you only throw out under a dollar's worth of ingredients.
I think that SAJ14SAJ listed some good examples, and that these certainly contribute to the overall taste. But I think there is yet another one, whose effect is strong enough to matter: rising.
Let's say that you coat 1 cm² of your tongue with a foodstuff. The more tastebuds are activated by a sweet molecule, the more is it evaluated as "sweet". First imagine your batter. It is dense, and coats all of the tastebuds on your tongue. Each of them is likely to register a few sugar molecules.
Now imagine the baked cake. It has air bubbles in it. If the plane of a cake cut has X% air bubbles by surface, then only 1-X% of your taste buds come in contact with the sweet cake. And the concentration of sugar molecules in the solid part of the cake surface is the same as the concentration in the batter, so you have the same number of sugar molecules per activated taste buds, but less taste buds activated. As cake volume contains lots of air, you also get lots of air bubble area in a cut. The effect is reduced by chewing, but by the time you have chewed the cake very well, it has also been diluted by lots of saliva, so now you have a much better coating, but less sugar molecules per taste bud.
By the way, this effect also occurs with salt in bread dough vs. baked bread, so I don't think there can be factors uniquely bound to the details of sweetness perception, as salt uses very different chemical pathways of being tasted.
Best Answer
You can make pretty much any bread-like substance into french toast (slice the bread, dip or soak in eggs mixed with a little milk, then shallow-fry in your choice of fat) or bread pudding (cube the bread, if necessary spread it out to dry and/or toast it, pile it in a baking pan, cover in a milk + egg + sweetening mixture, bake). Heck, if you're feeling really decadent (or you can't make up your mind), you can make french toast bread pudding: fry the bread, then make it into bread pudding.