TL;DR – no worries, it’s normal. Just wash it.
When unpacking a new shirt or hoodie with a direct-to-garment (DTG) print, you might notice a vinegar-like smell or an off-white residue. Don’t worry, that’s not unusual – it’s from a fixation agent applied during the printing process and it’s not permanent.
Fixation agent (sometimes known as pre-treatment) is used for all DTG prints across the industry. It helps the ink bond with the fabric, and without it, the ink would flake off the garment.
The solution is simply to wash the garment! Neither the residue nor the smell is permanent and both should go away after one wash.