The promotional mugs can be considered a no brainer promotion, providing obvious utility. With the transcend logo printed onto the mugs, they provide marketing and advertising for the brand when used.
However a relatively big purchase item such as a hard drive, offering a pair of mugs may be too simplistic to sway consumers to purchase your brand.
Suggest Transcend use something more creative like:
They could stay with mugs, but use something like colour changing thermochromic ink for the logo, offer silicone lids, amend the shape etc…
Staying on the drinks theme, they could also do something like our Octopus or Coolzee beer promos.