There is a rare event that lets you get rid of up to 3 cards from a random selection of your cards.

Must be real rare if I havent found one in 5 runs, lolz. Each one lasting till mid of the 2nd week.

I feel like they should not give so many cards in the first place. The starting amount is just fine and I find no reason to need more. you should only get cards you buy with already stick on stickers.