Heat the oil in a small saucepan over medium heat. Add the shallots and garlic and cook for 2 minutes, until soft and fragrant, stirring regularly. Add the tomatoes, smoked paprika, salt, pepper, and sugar. Lower the heat to medium-low and cook for 30 minutes, uncovered, stirring from time to time, until the mixture is thick and the juices have evaporated. Transfer to a bowl to cool. (This can be prepared up to a day in advance. The tomato confit can also be mixed until smooth and used as a spread or dip.).
Drain the sardines and pat with paper towels to remove excess oil. Mash together with a fork and divide into four equal portions. Slice off and discard the crusts of the bread (or leave them out to dry for a day and mix in a blender to make breadcrumbs), and toast the slices until golden brown.
Assemble the slices of bread into double-decker sandwiches, spreading each deck with fresh cheese and tomato jam, then filling it with sardines and arugula. Use a sharp bread knife to halve the sandwiches diagonally and secure each half with a toothpick if desired. Serve immediately, or wrap in wax paper and go eat on a patch of green somewhere.