It's been the strangest summer for sandwich lovers in the UK. We used to have them for lunch - now they're an option for dessert too.
For the second time in a matter of months, a butty with a sweet filling went viral on social media when supermarket chain Tesco unveiled a limited-edition birthday cake sandwich in early August.
It proved popular online, appearing in the top five of UK Google searches and dozens of TikTok less than 24 hours after it first went on sale.
What's in the birthday cake sandwich?
The sandwich is designed to taste a bit like a Victoria sponge cake and the recipe includes cream-cheese icing, strawberry jam and a sprinkling of sugar strands between brioche bread.
The reviews by TikTok users and news sites reveal different opinions. Some absolutely loved it, others could only manage a few bites, finding the sweet flavours overwhelming.
It wasn't the first sweet sandwich to hit supermarket shelves in the summer of 2025. To coincide with the Wimbledon tennis tournament in July, Marks & Spencer released a strawberries and cream sandwich, similar to Tesco's birthday cake variety.
What is a sando sandwich?
Many people in the UK will have become more aware of the "sando" when the strawberries and cream sandwich went viral.
Serving fruit in a sandwich is known as "furutsu sando" in Japan. When Japanese fruit shops opened parlours, similar to cafes, they sold desserts where customers could try the different fruit on sale. This included putting them in sandwiches, which became so popular it eventually became possible to buy sando in convenience stores.
Sando is usually served on sweet, white bread and can include fruit such as clementine and kiwi.
What makes food go viral on social media?
If an influencer has a big following on social media, something they try on camera can become hugely popular. This happened when food influencer Maria Vehera filmed herself trying a bar of Dubai chocolate which has been liked 7.2 million times and had well over 100 million views.
In the case of the birthday cake sandwiches, lots of people posted about them at the same time when they were released. After the viral trend of the strawberry sandwich, limited edition unusual fillings may still be in people's minds so soon afterwards.
Sandwiches are also something many of us eat regularly. They are relatable and easily compared to a more regular variety, such as cheese or ham. A 2020 study by the University of Leeds found that if something is familiar to us, we are more likely to share a post about it. Birthday cakes are also a regular sight in UK culture. We perhaps don't think of them as sandwiches very often, so that emotional reaction on seeing the two brought together can also make us share a post about it.
That mix of emotional connection, relatability and shareability could very well explain why we saw so much about birthday cake sandwiches when they went on sale. The only question is - should you have had one if it wasn't your birthday?
Other Side of the Story has more on viral food and drink in this collection.
This article was published in August 2025
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