Twilight-loves scented candles, her favorite food is either fruit salad or applejack's apple fritters, loves reading books on history, philosophy, or science fiction, favorite color is blue, had plenty of friends growing up but pushed them all away to pursue her studies
Rarity-vegan (most of the time, she will have fish here and there), shares recipes with fluttershy and applejack, all the clothes she makes are made with eco-friendly fabrics, loves cats, played dress up with sweetie bell when she was little, favorite food is salad or brownies, favorite color is either red or lavender, didn't have many friends growing up so she threw herself into fashion
Pinkie-makes cupcakes for her friends all the time, really big on parties, sugar addict, plays video games with rainbow, loves kids movies even as an adult, good with kids, has really good intuition, lets rarity and fluttershy style her hair sometimes, doesn't have a favorite color, has always been a social butterfly
Applejack-likes baking with her friends, loves animals but would never admit it, loves growing plants, helps apple bloom with her hair in the morning, favorite food is apples or pears but she would never tell her family, favorite color is green, didn't have many friends outside of her large extended family so she was never lonely
Fluttershy-loves foraging in the woods, recovered from an ed, rarity helps her with her makeup, makes friendship bracelets for everyone, likes to paint her nails, gives good advice, loves cuddles, favorite food is seaweed or pasta, goes flying with rainbow and twilight sometimes, rainbow was her only friend growing up
Rainbow-loves kids, dyes her hair, her original hair color is red like her mom, loves buying gifts for her friends, has anxiety, loves soda, favorite food is pizza or apple cider, favorite color is light green, worries about her friends a lot more than she lets on, everyone wanted to be friends with her but she was very picky about friendships but she was close with fluttershy growing up
note: i didn't add gender sexuality or pronouns hcs because i don't have a preference on those for any of them. these are just my opinions and you can headcanon whatever you want about them!!!