A Halloween-themed installment of the flagging “V/H/S” franchise is obvious to the point of redundancy: Both have become annual celebrations of horror-related kitsch, “scary” as a means of self-classification but increasingly safe — even comforting — in execution. The CEO of a beverage company is product-testing their new cola, Diet Phantasma, every can of which seems to contain a demon from hell. Guess who’s waiting for them inside a house that none of the other, younger kids on the block can seem to see? At least “Fun Size,” directed by “Too Many Cooks” auteur Casper Kelly, has the chutzpah to mess with expectations. Want to stay up to date on IndieWire’s film reviews and critical thoughts?