Battle Gyms Together
Assuming you’re a level 5 or higher (if not you’ll need to level up), you can go around to local gyms and battle your way to the top together. After earning your XP and leveling up together, you can put a cherry on top of all your hard work conquering all the gyms and go out for a drink.
And, you can compare stats, plan another battle-date and spend a little time reviving and healing any of your Pokémon that may have lost. All around fun, neh?