I am not alone! I thought I was the only one who could tell if spoons had been used in different drinks.
Dh tends to drink coffee, very very rarely drinks tea. I don't drink coffee at all, only tea. If dh makes a drink each and stirs my tea with either coffee dust on the spoon or a tiny bit of coffee on it from having stirred his cup before mine I can always taste the coffee in my tea.
Not having seen him do it I asked him if he had stirred his coffee before my tea and used the same spoon without washing it. He said he had, how did I know? I told him I could taste the coffee in my tea.
He was a bit sceptical, so every time it happened after that i would mention it to him so he knew I could taste it. He eventually accepted I could taste it so doesn't do it any more. (I have wasted the odd cup of tea before when the coffee taste was too strong to drink it so he eventually stopped doing it.)
Whenever I make drinks I either use different spoons or rinse/wash the spoon between mugs. I can't stand the idea of contamination between the drinks.
(Also, he couldn't deny doing it most of the time either. I realised, as we don't have matching crockery for everyday drinks, the mugs he use sound different to the mugs i use when being stirred. His tend to be bigger or tapered towards the bottom, mine more a standard size and straight sided, different sounds. When he stirs them and the kitchen door is open I can tell if he stirs his mug first and then immediately stirs mine - no time to clean the spoon. If he uses two spoons I can hear if he's put two down, he's noisy. Also, if using two similar/exactly the same mugs, it sounds different when stirring tea to coffee. Anyone else noticed that or am I just odd?)
Boy, I must be terrible to live with.