This page offers a guide on how to get Dew in My Time at Sandrock. Dew can be used to make Water barrels to fill up your Water tank when you run out of water.
How to Collect Dew
You can collect Dew by chopping at bushes and small cacti (don’t chop the big ones!) or by collecting plants in the area around your workshop. You’ll need 10 Dew to make one barrel of water at the worktable. One barrel of water is not a whole lot and won’t last long if you have a few machines operating, so you’ll either need to harvest a bunch of Dew, or later in the game you can build a Dew Collector.
How to Make Water Barrels with Dew
If you don’t want to waste too much of the town’s water supply, you could use Dew to make your own water barrels!