Do they say “weight snacks.” “I don’t have to weigh yet”? Their voices sort of overlapped.

Weigh in snacks

It might be "Wait Snacks" as a play on words that the family is doing? (Wait to eat, etc...) It could also be "Weight Snacks" referencing some kind of physical sport: Wrestlers for example are split into weight categories and pre-season people will always try to bulk up or bulk down to get into a specific tier. Given that they say "Weigh in", I'm inclined to think it's this one.

They are saying "weigh in" snacks. Note that the youngest is wearing a wrestling hoodie. They're likely getting ready for a wrestling tournament and want some snacks to eat after they weigh in.

But there are subtitles? ... The youngest one says that she doesn't have to wait. Her sister might have to wait an hour to eat or something, but she doesn't have to wait. At the end, he says, "But sis, you gotta cut a little weight to...". This is, "But \[older\] sister, you have to cut \[lose, drop\] a little weight to \[have the right weight for the wrestling team\]. I'm guessing, but she looks like a wrestler. So, she has to wait to eat, because she's on a diet. She has to "weigh in" before her event so that she will be in the right "weight group" and won't have to wrestle someone heavier.

Weigh in. As in being weighed for sport weightclass

This feels like rage bait. The girl on the left is wearing a team wrestling hoodie. I'm assuming the girl on the right wrestles, too. Weight classes and weighing in under a specific weight are required. Wrestling and eating disorders go hand in hand. I knew a guy who wouldn't swallow his saliva on weigh-in days. This is why I played basketball.