I went to the convenience store with my friend and blew some money on junk food.
My friend and I went to the convenience store and wasted some money on sweets and snacks.
ーI went to the convenience store with my friend and blew some money on junk food.
「友達とコンビニに行って買い食いをした」
to blew some money on junk food で「買い食いをする」と言えます。
to blow money on で「ばかなことに・つまらないものにお金を使う」
ーMy friend and I went to the convenience store and wasted some money on sweets and snacks.
「友達と私はコンビニに行ってお菓子やスナック菓子を買い食いした」
to waste some money on sweets and snacks で「買い食いする」とも言えます。
to waste money on で「〜に金を無駄遣いする」
ご参考まで！
カナダ 
