I used coffee, blackberry tea and home-made blueberry syrup.
I recommend letting the different dyes to boil when putting the bundles into them, leaving them like that for a few seconds, then pull the pots of dye from the stove and covering them, leave the bundles to rest in the liquids for 20-30 minutes. Adding a spoonful of white vinegar helps the fabric to absorb and keep the color.
Remember, your yarn needs to be 100% natural in order to absorb these natural dyes.
You can then use the yarn to do different projects. I used mine to crochet tiny little hearts, but you could even dye a larger amount and crochet/knit up a cowl or why not, even a cardigan! Totally up to you!