Try the new Tuna Creations by Starkist. Foil packets, stores flat in a briefcase for easy travel. Very little water (or oil). Plain tuna comes in a larger serving size, but the flavored ones kick ass (35 gr of protein).
Smoked is awesome.
Lemon Pepper is decent.
Herb Garlic is decent.
Sweet and Sour sucks.
About $1.90 per packet - but considering ease of use, portability, flavor, and storage (no refridgeration) - very much worth the money. I keep several in my briefcase to snack on whenever I get hungry.