The 28-year-old vlogger joined singer James Blunt, The One Show host Alex Jones, and TV presenter Alison Hammond to compete for the Star Baker apron in The Great Stand Up To Cancer Bake Off.
Sugg was chopping apples for his signature traybake when he cut his finger and fainted at the sight of blood.
Sugg said: “There’s always one isn’t there? I’ve just chopped the top of my finger off.”
As a medic approached to inspect his injury Sugg said: “I might have to sit outside for a bit. I’m feeling a bit...” He then collapsed onto the floor.
Coming round Sugg said: “Did I pass out? That’s a good start.”
The social media influencer - who lives with professional dancer Dianne Buswell who he met while competing on Strictly Come Dancing in 2018 - was making a traybake cake with biscuit spread.
But he asked the camera crew: “I did put it in didn’t I? Was it before or after I passed out? I think I did.”
This Morning presenter Hammond, 45, who found fame on the third series of Big Brother in 2002 approached Sugg’s bench to offer him something to eat.
She said: “I’ve just brought you some nuts just to make sure you keep your glucose sugar [up].”
Ahead of the show Sugg admitted on Instagram: “I have a bit of a bumpy start...”
But Sugg went on to receive a handshake from judge Paul Hollywood for his Signature Traybake, who told him: “Well thought through, well baked, and considering what happened to your finger - pretty amazing.”