I was working with a friend I've know since university
I was the developer, he was the salesman, and we had a central London office more or less to ourselves, as the head office in San Francisco stayed out of our way so long as we kept bringing in business.

I used to make drinks for both of us - tea for me and coffee for him, from one of those really big tins of instant Nescafe - and so I naturally began wondering what would happen if I started gradually upping his dose of caffeine. To start with he had two and a half spoonfuls per cup, so the first week of this experiment I upped that to three, then three and a half the next week, then four... By the time I 'fessed up to what I'd been doing he was a manic, jittery mess who was drinking coffee with twelve and a half spoonfuls in each cup.

He's never let me make a drink for him since.
( emvee cruor deo cruoris, Thu 16 Apr 2015, 16:15, 8 replies)

Yeah, you definitely couldn't tell if 12 spoonfuls of instant coffee had been used to make a cup.

(Baggenfrock get fucked, Thu 16 Apr 2015, 17:32, closed)

it's the way the spoon stands up

( drimble he'd been white, he'd been black, Thu 16 Apr 2015, 23:21, closed)

He claimed, in his defence, that he thought I was just bad at making coffee

( emvee cruor deo cruoris, Fri 17 Apr 2015, 8:15, closed)

INTERNET DETECTIVE SAYS YOU ARE LYING

(McChinaman banned, Thu 16 Apr 2015, 19:01, closed)

Did you also offer him a cappuccino and hock phlegm onto it?

( monster munch person, man, woman... camera... TV?, Thu 16 Apr 2015, 20:24, closed)

amazingly, I think this is the dullest lie you've ever told

(old man river possible lesbian, Fri 17 Apr 2015, 12:37, closed)

You're a worthwhile human being

( emvee cruor deo cruoris, Fri 17 Apr 2015, 15:41, closed)

I tried a similar thing with someone
He used to have 2 sugars in his coffee but announced he was cutting down to 1.
After couple of weeks I put him back up to 2, then 3.
By the time I'd got up to 4 I noticed him having a sip then subtly not drinking the rest claiming to have let it go cold and going to make another. I got bored of that game.
( thistle, Fri 17 Apr 2015, 14:26, closed)