Haha, it doesn't matter when you're in wilderness that you can't eat what you like such as cakes and sweets :) Strbske PLeso is full of shops and restaurants. There is a typical Slovak one where they serve greeeat dishes but the best place for gurmans is Tatranska Lomnica.
I was in this shop several times and usually bought *a lot* of food and *drink*.
What to buy: Everything. That's how our fridge looked like after we came home from the shop :)
What to pay: Nothing. It's everything so cheap!