I've been trying to find this BL series for the past 2 days. I remember watching a series that, one of them was dared to go after the other person. I'm not sure if it was the main couple plot or the support character's couple plot. I could be mixing it up with a non-BL series, but I could've sworn I watched a BL series with that in it. 

If you know it, or if I might be crazy, please let me know! <3

Haven't watch that many BLs, but maybe https://kisskh.at/768427-the-heart-killers?

I only watched 1 episodes of it (as it's not for me), but Dunk is being asked by First to chase and date Joong with a gift will be given to him if he succedeed (I forgot, car?)

Or maybe https://kisskh.at/788890-something-is-not-right? It seems like a match as far as I remember.