Combine all ingredients (including turmeric, if using) in small saucepan and bring to boil over medium-high heat, stirring to dissolve sugar.
Reduce heat to medium and simmer until jalapeños just soften, about 3 minutes.
Remove from heat and let cool completely, about 1 hour.
Using fork or tongs, transfer jalapeños to 8-ounce jar.
Pour syrup over jalapeños to fill jar, leaving ½ inch headspace.
Affix jar lid and refrigerate for at least 4 hours before serving.
(Candied jalapeños can be refrigerated for up to 1 month.)
