A very good idea spending a sunny day outside is to have a grill party. You can get small grills e.g. from Etola (found upstairs of Forum shopping mall) or disposable grills from bigger super markets.
Usually it's ok to grill in solid rock. This kind of places you find from Tervasaari (I have been grilling there), in Kallio there are several places and in Hietaniemen ranta (Hietsu beach). Someone might say, that "no, it's not like that, it's illeagal to grill in the city" but then if you want to be sure where to grill, ask the cops. I've been grilling around, and no one has said anything. Especially we have looked a place where others have been grilling too.
What to grill then? As I am vegetarian, I usually buy tofu and different veggies. I wrap them in foil with some herb and oil and yumme! Also there are different frozen stuff available, like vegetarian sausages (most of them include egg, so not suitable for vegans). If you are a meat eater I don't even have to write anything about sausages. Just go to the market and you'll understand what I mean....
|Disposable grill, ready in 15min! (pic from Rainbow.fi)|
|Cute mini-grill (pic from here)|