When there's a Sparkle effect around a character that's Sweating (post #4961776), or when a Sparkle effect is drawn over the sweat (post #4254581)
Could also apply if the sweat is rendered to look like it's glowing or sparkly.
See also
- Hot
- Sauna
- Shiny Skin
- Sparkling Sweat
- Sweaty Clothes
- Wiping Sweat
- Sweat for light sweating
- Very Sweaty for heavy sweating