Most people don't want to wear logo clothing, unless it's when they wash the car - how many give-aways do you have in the back of the cupboard?
But... with a cool design and the right price, customers might be persuaded to wear something that shows they've visited your cafe or food shop. It's another way to give bragging rights, apart from social media posts and messaging.
At my Cafe Troppo in Sydney back in the day, we sold thousands of t-shirts using a simple formula - a bright and breezy design, a low price of $10, and good merchandising. With a name like Troppo, it was easy to develop tropical designs with some discrete branding and a quirky message. We added a definition of the aussie expression 'gone troppo' - 'Troppo: A mental condition caused by too much time in the tropics'.
The real secret was the low-price and display - piled up in front of the counter, with S, L, XL and a couple of children's sizes. Grab and go - will we just add that to your bill?
My best Troppo T-Shirt experience was being in the London Underground and seeing a local wearing one. Truly international promotion, long before Facebook and Instagram!
Decide who you are selling to. Figure out the gender, age, and interests of your ideal customer. Once you figure all that out, you can then focus on serving that particular demographic, which will be immeasurably easier than trying to serve everyone.