sun （动）晒太阳
your 你的
buns (大概是写错的 bums=屁股 （俚语））
in hell 在地狱
骂人话，和 damn you/burn in hell/go to hell 意思差不多 = 到地狱去晒你的屁股
再update 以下：
bun3 (bŭn) （名）（俚语） One of the buttocks. Often used in the plural：buns
The part of one's back on which one rests in sitting. buttock (used in plural)， posterior, rump, seat. Informal backside, behind, bottom, rear.
来由古代苏格兰方言： hind part of a rabbit or squirrel, from Scottish Gaelic
现代英语俚语一般用 bum=屁股
