How to add water to sand without flooding?

Basically what the title says. I know we aren’t supposed to spray the sand because it can cause flooding. I’ve been adding wet sphagnum moss and that worked for a while but now the sand is way too dry again (I wasn’t super on top of it lately due to having a baby and being in the hospital for four days after a c-section). What’s the safest way to add moisture back to the substrate?