The best replacement for sack is bag.

The best alternatives to sack are rated as following:
★★★★★  bag
★★  6 sack
★★  sac
★★  swaddle
★★  6 sack concrete
★  tackle for loss
★  blitz
★  sack
★  comfy sack
★  tfl
★  shaft
★  tackle
★  lovesac
  blanket
  hatchet
  swaddling
  compression sack
  yolk sack
  nut sac
  love sac
  sleeping bag

Your alternative for sack is not listed? Suggest!
Speaking about sack, one probably shouldn't forget about sleeping bag.

Other search terms related to sack and their ratings are:
★★★★★ sleeping bag
You have in mind a companion for sack and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sack in all years. Click on graph for more.
sack
bag
6 sack